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You can search through the full text of this book on the web at |http: //books .google .com/I Harvard University TRANSFERRED TO HARVARD COLLEGE LIBRARY/— V' TIMBER ITS STRENGTH, SEASONING, AND GRADING IMIIIJ|IIIII([[IIIIII|^|IIIII|||IIIIII|||IIIII|I|IIIIII,|| IIIIIIIIIIIIII|IIIIIIIII|IIIIIIIU1IIIIIIII11IIIIII[)I1II1IIII[ 'ykis Qrobo-JJillBook Qx Tm PUDIISMCRS OF bOOfCS POR^/ Coal Age ^ Electric Railway Journal Electrical Wxld ^ Engineering News-Record American Machinist ^ Ingenierfa Intemacional Engineering 8 Mining Journal ^ Power Chemical 6 Metallurgical Engineering Electncal Merchandising m iii l l l iii i iiil l lii i ii i llliiii ill i iiii i ii ii ii i i iiii i iiiii i iii i iiiilllllllllllllllllllln^^ TIMBER ITS STRENGTH, SEASONING, AND GRADING BY HAROLD S. B ETTS, M . E. FOREST 8EBYICE, V. 8. DEPARTMENT OP AGRICULTURa First Edition Second Impression McGRAW-HILL BOOK COMPANY, Inc. NEW YORK: 239 WEST 39TH STREET LONDON: 6 & 8 BOUVERIE ST., E. C. 4 1919 I ■■ -^^^^.it^ Copyright, 1919, by the McGraw-Hill Book Company, Inc. THfl MXFIiXD FKBSS "TOKK FA, AFFECTIONATELY DEDICATED TO THE MEMORY OF MY BROTHER Norman DeWitt Betts PREFACE This book is intended primarily for engineers, manufacturers and users of lumber and of various special classes of wood material, and students of engineering and forestry. For such structural materials as steel, concrete, etc., there is a wealth of technical information in readily accessible form. Of wood the same can not be said. It is hoped that the present volume will serve to some extent to supply this deficiency. The data given are derived almost entirely from tests and in- vestigations on the mechanical properties of wood made by the Forest Service of the U. S. Department of Agriculture. Various bulletins, circulars, and papers of the Forest Service, especially those prepared by the author and those with the preparation of which the author was closely concerned, have been drawn upon freely. Most of the diagrams have already appeared in Depart- ment of Agriculture publications. The author wishes to acknowledge his indebtedness to the members of the Forest Products Laboratory and the Office of Industrial Investigations of the Forest Service for the use made of their publications and for assistance in the preparation of the text, and to thank the various associations for the data they have supplied. Special thanks are due to Mr. Rolf Thelen for his review of the text. Harold S. Betts. vu CONTENTS Page Preface vii Chapteb I. Timber Resources of the United States 1 II. The Strength of Wood 10 Results of tests on North American woods. Relations indicated by tests. Methods of test. III. Effect of Moisture and of Preservative and Conditioning Treatments on the Strength of Wood 27 Effect of moisture. Effect of preservative and conditioning treatments. Tests on treated southern yellow pine and Douglas fir. Methods of treatment. Methods of test. Results of tests. Stringers. Small pieces cut from stringers. Special tests in small pieces. Deductions. IV. Strength of Wooden Products 43 Structural timbers. Strength of the principal structural species. Characteristics affecting the strength of timber. Density. Rate of growth. Direction of grain. Moisture. Sap wood. Defects. Position of pith in cross section. Characteristics affecting decay in timbers. Conditions in the wood itself. Agencies that destroy wood. Relations indicated by tests of structural timbers. The grading of structural timbers. Classification of defects. Various grading rules. Working stresses for structural timbers. Telephone poles. Cross-arms. ix X CONTENTS Chaptsb Page Packing boxes. Compression and drop tests. Tests by a revolving drum machine. The machine. The boxes tested. Deductions from tests. Nailed boxes. Wirebound boxes. Wooden vehicle parts. Hickory buggy spokes. Oak and hickory buggy shafts. Maple and hickory wagon axles. Oak, southern pine, and Douglas fir wagon poles. Douglas fir and southern pine cultivator poles. Deductions from the tests of vehicle parts. V. The Seasoning op Wood 125 Importance of proper seasoning methods. Fiber saturation point and shrinkage. How wood may be injured in seasoning. Checking. Casehardening. Honey combing. Warping. Collapse. Air-seasoning. Cross ties, poles, and sawed timbers. Lumber. Rules for piling lumber. Kiln drying. Types of kilns. Preliminary treatments. The process of drying. Storage of dried lumber. VI. The Grading of Lumber by Manufacturers' Associations. . 162 Principles of lumber grading. Manufacture and distribution of graded lumber. Hardwood lumber grading. Hardwood associations. Comparison of rules. Softwood lumber grading. General character of the rules for softwoods. Description of typical rules for softwoods. VII. Lumber Produced and Used in the United States 200 Lumber produced by mills. Lumber used in the manufacture of wooden products. Index 225 TIMBER : ITS STRENGTH, SEASONING, AND GRADING CHAPTER I TIMBER RESOURCES OF THE UNITED STATES Forest Regioks op the United States — Types op Forests — Estimates of Stand — Diagram and Table Showing Stand by States and Species — Timber in Public and Private Ownership — Forest Renewal — Shifting Cen- ters OF Production — Change in Species Forming Bulk op Lumber Cut — Future Timber Supply op the United States. The forest regions of the United States are shown in Fig. 1. Slightly more than one-half of the supply of timber is in the Pacific Northwest (Washington, Oregon, northern Idaho, western Montana, and northern California) ; about one-fourth of the total amount is in the Southeast; the remainder, except for a small proportion in the Rocky Mountains, is distributed throughout the former centers of production, the Lake States and the North- eastern States. Five groups of States cover the natural tim- bered areas of the country: the Northeastern States, the Southern States, the Lake States, the -Rocky Mountain States, and the Pacific States. In the forests of the two groups last mentioned practically all of the timber-producing trees are conifers. In the first four groups the timber-producing trees are both conifers and hardwoods. The first heavy timber cutting in the United States was in the white pine forests of the Northeast, and the original stand of white pine has been largely cut out. The present stand in the northeastern States is mainly spruce, second growth white pine, hemlock, and hardwoods. In the Southern States there are four different types of forests, broadly distinguished according to their elevation above sea 1 TIMBER RESOURCES OF THE UNITED STATES 3 level. The swamp forests of the Atlantic and Gulf Coasts and the bottom lands of the rivers furnish cypress and hardwoods. The remainder of the coastal plain from Virginia to Texas was originally covered with southern yellow pine. The plateau which encircles the Appalachian Range and the lower part of the mountain region itself support the pure hardwood forest. The higher ridges are occupied by conifers, mainly spruce, white pine, and hemlock. The Lake States still contain large hardwood forests in their southern portions. In the northern part are coniferous forests made up of the rapidly diminishing white pine and of tamarack, cedar, and hemlock. The principal timber trees of the Rocky Mountain forests are western yellow pine and lodgepole pine. The Pacific forests, which contain the largest amount of timber still standing in the United States are largely made up of Douglas fir, western hemlock, sugar pine, western yellow pine, redwood, and cedar. A number of attempts have been made to estimate the amount of standing timber in these various regions. The most authentic estimates are given in Table 1 (p. 5). It will be seen that they vary widely but that in spite of the continued cutting of our timber the more recent estimates of what is left are larger than those made earlier. The latest estimate^ gives the total amount of standing timber in the United States suitable for the manufacture of lumber as 2,826 billion board feet. The original stand has been esti- mated at 5,200 billion board feet. Of the difference, it is probable that about one-third has been destroyed by forest fires, one-third lumbered, and one-third wasted. Figure 2 shows the estimated stand of the principal species in the various States. The size of the squares indicates the amount of standing timber in the various areas, which in some cases include a number ^ Paper presented before the International Engineering Congress, Sept., 1915, "Structural Timber in the United States," by H. S. Betts and W. B. Greeley. The estimate in this paper is taken largely from a report of the Bureau of Corporations of the Department of Commerce on "The Lumber Industry," and the Report of the National Conservation Commission. These estimates include, for the most part, only timber of sawlog size, as determined by current requirements. A figure representing the total forest resources of the United States, including fuel, pulpwood, etc., would be materially larger. TIMBER RESOURCES OF THE UNITED STATES 5 1 6 TIMBER < OQ I OQ A OQ g O 00 88 o g *-< I-* « u 3 o t iH 0. QQ 11 O W^ ►< -, 88 S 00 1 s >>« 1^ ^S, a h* IH ^1 o s ^ fe" c^ ^S ■Ml-4 ca lO ^^ ^ o ^ tf ^ d ^ lis •z: 5 CO ►J * ft d ther How ine 04 3 ® ft o >>** OQ ^ d S »^ «-4 Q- 1 d o B S OQ co«>oa»^«ooiHOC4io>0'^^i-iaooao«oo>ot*a»^c4C90ooai'^a» CC40000C^ t^-Ti4C0 1-1 ^rHiC U)C40) «0 C4 C4r«^ CO iH iH iH -N -csioco^io •eo^^^oo^ot*t*ooooooos • N -OiO ••^CO • 00 -CS -OCOOtI* 1-4 'IQ • 1-t •iOi-iO^00®C0"^i-i<0^t»t» . iH -ooco •»-<• wcoeoOTj* • • 00 O) t« O) ^Ni-i eo oJ»-«Nooco «o •CO •N ... . -co • O O N iH M • • • • • • iC • CO • • • • • ;••••••• • ^ • oo . , ,^ .............. ........ .^ ..................... . •00 • lOco • • ..«>••. • • 'ONOS • • . .OJ . • • N • 1-teo • • • ^ • • • • • ..©<... • • • • • ..«>•• >t*co it* •OCO i-iN«0 :« : -.6 ■O ' -iH ■CO ■^ d ' voo ■cod •CO •00 ■U3 ■d OS •o oa> •N •«-! •OS •CO ;0 -O •eo -ci ••O • »o 00 CO CO di>»-H "3 CO IN CO »o ■ .„„'S'5pjfi9 r^ r- — r- r- rm ^ ' gg Q) Z 4 4 aS.S.«4.9.S O'qJ V V ^ ^ V 5 5 TIMBER RESOURCES OF THE UNITED STATES 7 w^ Sugar pine 00 OS, t* o Eh 49 o «.J4 go O o CO - O flS G,-i d ^ « « GO a h u © ^ u o « o -J iO sa nil"* ^ ^ .•^ 0) A V ►^ >» CO o >> GQ C9 I OB coor«eoooco>0(Oioo-^kor^csio o iH ^»0 CO OOtHiHrHOJ^COC^ C^ »o eo 00 »«5 n a o p »Oi-i -ooeoos •OO -NO -co® • C^O -tOOOO •-« -CO '•^a -t^io -neo • •»OM • 'CO^ • CO t* «-! o eo t* OON • • 't^CO • • O • •''^ • -OO • ' \m'% r - ■ F . ^J■ 00 CO 8 4 •O Ot!* •OSO -o ■rH lOi-t -rHOO ■■^ • 1-t 'y^ . .r? • • •© • -00 • -NCO • ■ ••f • • -M • -o • -ioci • ■ -r-l T-t . .Qi ............ . • d *•••••• • •iH . . .O • -CI • -CI • • • - . . ! -c^ • -d ■ -o • • • • • N • ^ . . . •d ■••••••• "-j •• • \^ '.'.'. \ \ \ '. \ '.-^ '.'. \ . to \n • • ' •CO • • »o . • • 00 d d o ' *CS| • !(M ! !«c» • ■00 • • o • • • * • • • • • • ■ • • • • : :8 : •CO 1 •CO • ■0> • •o . .1-4 • • eo CO lo ^1 lOOS I h- iC o o 00 o CO ■*i> OQ eS o d >> , blu Ath, BTt Aih.K Amb, Or Aah, wli Aah, wl Ath. V, AMpea C tmndl ' Buokthi , Cbattni Clwatni Cbinqni ohpy» ' Cottoni Cottom triotii ' Cuoiiml ^ r-t.) ^ DoBwm , florid Hardw ItlOHH HwdoMi Shook ^ Sh«»iD( S CsQUnOD «i««^ ^ ■Sffir s P ua DC 04k -100 Loadn- mi it! di>m«tor IMmtive tooftk Oik -100 Work to iMIldiDI boUtlvB ■hockrs- C^^k^OO Ks strengtE oompwed O^^OO 21 22 23 es IflM 84 IM 1.276 9S 121 1.088 622 83 . 71 90 1,B21 60 1.097 84 lOS 1.54S 63 1.227 1,031 S4 79 71 1.072 82 86 102 1,058 81 171 1.3S« 104 1S3 I.ie2 89 272 1,212 1.237 S3 1.270 97 23S 1,282 08 181 171 1.031 79 1,207 208 l.*27 109 262 l,3S8 104 1,396 107 126 1.262 07 2S6 1.421 109 1,246 B6 138 1.263 07 1.440 110 87 100 1.374 108 126 1.272 97 M 1.669 128 rt FoUomni SIteel A) Hare Comin iffi - Oak, wil Oak, yel Oak, yel Oaaseor Pecan (I Peraimm Rhodode dron u Sassafrafl Servicelx densis) Silverbel carolic Sourwoo Sumach, Sugarbei Syoamor Sycamore Umbrell Walnut, Willow, Willow, Willow. lasianc Witch h ana) . Yellow tulipif* ReUtive StiffMM compared to oak Oak -100 17 Load re- 9uired to uibed a 0.44 inch ball one-hall its diamet«r 18 Relative hardncM compared to oak Oak -100 19 Shock reeistiag ability J^ Work to maximum load in bending 20 Relative ■hock re- sisting ability compared to oak Oak- 100 Shearing strength paraUel to g grain Shearing strength 21 22 Relative shearing strength compared to oak Oak -100 98 93 86 101 104 104 67 69 125 89 100 62 62 74 89 91 108 49 37 78 85 92 978 1,057 • • ■ • 2.037 1.308 1,279 864 524 1.244 470 728 590 739 580 638 503 899 383 334 501 977 338 93 101 • • • 194 125 122 82 50 119 45 69 56 71 55 61 48 86 37 32 48 93 32 8.8 11.7 13.2 37.9 14.6 13.0 12.1 7.1 16.2 8.8 9.8 10.8 12.0 7.1 y.9 8.3 14.6 8.7 12.9 10.8 19.5 5.6 66 88 99 285 110 98 91 53 122 66 74 81 90 53 59 62 110 65 97 81 147 42 1,184 1,179 1.481 1,474 1,240 952 1,256 931 1.157 • • • • 1,049 1,001 990 827 1.216 685 561 866 1,118 787 NoTB.'P The strength value given (modulus of elastioity in bending) is for i^een wood. Thaa strength value is about 25 per cent, greater for air-dry wood than for the green. ) The strength value given (side hardness) is for green wood. It is an (.^ avera^ of the values for radial and tangential hardness. This strength value IS about 33 per cent, greater for air-dry wood than for the green. i4 CB.4& a ) The ability of the wood to resist shock is a combination of strength and toughnc The strength value given (shearing strength) is for green wood. ^ It represents an average of the values for radial and tangential shearing strength. This strength value is about 50 per cent, greater for air-dipr wood than for the green. The shearing strength of kiln-dried wood is greater than that of aiivdry wood. 23 91 90 113 113 95 73 96 71 89 • • • 80 77 76 63 93 52 43 66 86 60 (8Am( D. — Innrt Fottotoing 8hMi O <" Conif atufoM HudMia 6h«k ). 4T 781 00 Rr, Dm f • • 28 21 25 33 33 35 26 27 36 110 Shock reaiating ability Work to maximum load in bending 20 5.1 4.9 6.0 6.3 5.3 7.6 8!9 8.1 8.1 7.0 8.5 7.5 5.8 « • • 8.7 5.0 8.1 5.1 4.9 4.3 6.0 5.2 • • • 5.9 5.0 4.8 6.0 6.2 6.4 6.6 5.4 7.2 20.2 Relative shock re- aiating ability compared to oak Oak -100 Shearing strength rtOlel grain toi Shearing strength 21 38 37 45 47 40 67 67 61 61 53 64 56 44 » • • 65 38 61 38 37 32 45 39 ■ • • 44 38 36 45 47 48 50 41 54 152 22 ReUtlve shearing strength oompared to oak Oak -100 23 710 679 670 665 714 1.066 1,150 1.062 1,006 1.034 949 936 776 708 1,071 708 955 711 662 696 705 674 • • • • 644 569 615 768 764 777 630 691 863 1,621 64 62 61 51 55 82 88 81 77 79 73 72 59 54 82 54 73 54 51 53 54 52 49 44 47 69 58 59 48 53 66 124 iSheet F.—Intert Following Sheet E) THE STRENGTH OF WOOD 11 Small clear specimens were used. Each line of the table repre- sents the average of tests made on pieces cut from five typical trees from a single locality.^ Since there is considerable varia- tion in the strength of wood from individual trees of the same species, the results should be taken as indications rather than as fixed values. Table 3 gives average values obtained from tests on green material. The values for dry material would be higher, as in- dicated in the accompanying notes. While it is true that the properties of all species are not changed in the same proportion by drying and that all the properties are not equally affected, nevertheless the converting factors given in the notes will in- dicate with sufficient accuracy for most practical purposes the strength to be expected in the dry material. The first column in Table 3 gives the common and botanical names of the species. Since many species have a number of common names, some of which may be used for several species in different parts of the country, the botanical name is needed for positive identification. The locality where grown as shown in the second column of Table 3 should not be given too much weight as an indication of strength or weakness. The influence of region of growth on the properties of wood is generally over- emphasized. The columns numbered 3, 4, and 5 give the weight per cubic foot in three conditions of moisture — green, air dry, and kiln dry. The weight in a green condition was determined at the time the logs were sawed into pieces for test. The various species differ largely as to the wetness of the green wood. . The hardwoods as a rule do not exhibit any considerable variation in moisture with the position in the tree. The conifers, on the other hand, show a wide variation in moisture content between the heartwood and sap wood and in some instances between the upper and low:^r parts of the tree. Tamarack and cypress, however, have a comparatively uniform moisture content throughout the tree. Sugar pine and western larch are frequently very heavy, because of moisture in the former and resin at the butt in the latter. Longleaf pine and some other species have a very low moisture content in the heartwood, while the sap wood is very wet. When this is the case, young thrifty trees with a large propor- ' The averages for a few of the species listed in Table 3 are from less than five trees. 12 TIMBER tion of sapwood are much heavier than old over-mature trees with a small amount of sapwood. The weight in an air dry condition was determined after the test material had dried to constant weight under shelter. The moisture content under such conditions is generally from 12 to 15 per cent. It varies with the part of the country in which the drying or seasoning takes place. An air dry condition in Douglas, Arizona, would mean a considerably lower moisture condition than an air dry condition in Seattle, Washington. The weight in a kiln dry condition was determined by adding 8 per cent, to the weight of the bone dry wood.^ Of course, kiln dried material may be dried so that it has more or less than 8 per cent, moisture, depending on conditions in the kiln. Eight per cent, is con- sidered an average moisture content for kiln dried wood. In the determination of the figures for specific gravity based on volume when green (column 6), the test specimens are weighed and measured when green. Their oven dry weight is then com- puted by dividing the weight when green by one plus the pro- portion of moisture. Specific gravity based on volume when green is unaffected by the shrinkage of the wood. Specific gravity is the best criterion, except actual strength tests, of the strength of the clear wood of any species. It has been found that in oak, more than in any other species or group of closely related species, pieces of the same density may vary widely in mechanical properties. Occasionally very dense pieces of oak are for some unknown reason low in strength; but in all species, specimens of low density are invariably weak. The per cent, of shrinkage that occurs when a piece of wood is dried from a green condition to an oven dry or bone dry condition is shown in the columns numbered 7, 8, and 9. All shrinkages are expressed in percentages of the original or green dimensions. In practice, wood is seldom if ever dried to an oven dry condition. It is generally either kiln dry or air dry. The shrinkage to be ex- pected in drying green material to a kiln dry condition may be taken as 75 per cent, of the shrinkage from a green to a bone dry condition; and the shrinkage from a green to an air dry condition as 50 per cent, or one-half the shrinkage to a bone dry condition. Column 7 gives the shrinkage in volume, omitting longitudinal shrinkage, which is negligible. Columns 8 and 9 give the shrink- ^ For accurate calculations the swelling from to 8 per cent, moisture and the consequent reduction in specific gravity must be taken into account. THE STRENGTH OF WOOD 13 age in the radial and tangential directions respectively. The radial shrinkage is roughly one-half as much as the tangential shrinkage. Radial shrinkage is a measure of the change in width of a quarter-sawed or edge-grain board. If such a board of Douglas fir 10 inches wide were dried so that the moisture was reduced from 30 per cent, to 15 per cent, (green to air dry con- dition) the decrease in width would be about ^e inch. Tan- gential shrinkage is a measure of the change in the width of a flat-grain board. In a 10-inch flat-grained Douglas fir board the decrease in width when dried from 30 per cent, to 15 per cent, moisture would amount to about ^e inch. Columns 10 and 11 show, respectively, the modulus of rupture or breaking strength in bending in pounds per square inch and the strength compared to oak. The modulus of rupture is a measure of the abiUty of a beam to support a slowly appUed load for a short time. Safe working stresses for carefully selected structural timbers, such as floor joists, stringers, etc., with all ex- ceptionally light pieces excluded, subjected to bending in dry interior construction, are about one-sixth the modulus of rupture values given in Table 3. The values given are for green wood. The modulus of rupture for air dry wood is about 50 per cent, greater than that for green. For kiln dry wood it is about 100 per cent, greater, or twice the green value. This increase in strength due to drying does not apply to comparatively large structural timbers, in which the defects induced in the drying process, such as checks and shakes, frequently offset any increase in the strength of the wood itself. Columns 12 and 13 give, respectively, the crushing strength for green wood in pounds per square inch and the strength com- pared to oak. For air dry wood the crushing strength is about 60 per cent, greater than for the green, and for kiln dry wood the strength is about 100 per cent, greater, or twice the strength of the green. The maximum crushing strength is a measure of the ability of a short block to sustain a slowly applied load. It is important in calculating the strength of short colmnns. A safe working stress is about three-tenths the crushing strength as given. ^ Columns 14 and 15 give the strength in compression per- pendicular to the grain and the relative strength compared to. oak. Fiber stress at elastic limit is the value given. It * In dry interior construction, and with light weight pieces excluded. 14 TIMBER represents the greatest stress that can be applied without injury and is used in computing the proper bearing area for beams, raih-oad ties, etc. Two-thirds of the fiber stress given in Table 3 may be used as a safe stress in dry interior construction. Columns 16 and 17 show the modulus of elasticity in bending in 1000 pounds units and as compared to oak. The modulus of elasticity is a measure of stiffness and is used in calculating the deflection of beams. A high modulus of elasticity means a high degree of stiffness with but little deflection. One-half the values given in the table are recommended for use in the design of structures on account of variations in the quality of timber and inaccuracies in workmanship in fitting together the various parts. Columns 18 and 19 show the hardness as indicated by the load required to imbed a steel ball in the various species of wood and as compared to oak. Hardness is important in flooring, handles of various kinds, paving blocks, vehicle material, etc. There appears to be no consistent difference between the hardness on a radial surface and on a tangential surface, and both values are averaged and tabulated as "side hardness." End hardness (not given) is usually slightly greater than side hardness. Columns 20 and 21 show the work to maximum load in bending in inch pounds per cubic inch and as compared to oak. The work to maximum load is a measure of the shock-resisting ability, or combined strength and toughness. It is important in estimat- ing the relative fitness of woods for uses where they are subjected to sudden loads as in wagon or automobile spokes or axe handles. Hickory and osage orange are woods that rank especially high in shock-resisting ability. Columns 22 and 23 show the shearing strength parallel to the grain and the shearing strength compared to oak. Shearing strength is important in beams which are likely to fail by shear- ing lengthwise so that the upper half slides on the lower half when the beam bends. RELATIONS INDICATED BY TESTS 1. The density or dry weight of wood is a measure of its strength. 2. Each annual growth ring is made up of a comparatively heavy band of summerwood and a lighter band of springwopd. The greater the proportion of summerwood, the greater the weight and strength of the timber. THE STRENGTH OF WOOD 15 3. No diflferences in mechanical properties due to a change from sap to heart have been found. As a general rule, in species which show a variation in the mechanical properties with position in cross sections, there is a certain age when the best wood is produced. In such species the age and thrift of the tree deter- mine whether heart or sap is the better. For example, in a young, thrifty hickory the sap wood is usually the better; while in a large, over-mature tree of the same species the heartwood is the better. 4. Exceedingly rapid or slow growth in conifers has usually been found to be attended by lack of density and inferior mechanical properties. 5. The effect of location of growth on the nature of the timber is very complex. Variations attributed to difference in locaUty of growth are frequently exaggerated. These variations are generally apparent in the difference in density of the wood. 6. Trees growing close together and apparently under the same conditions occasionally show a difference in their mechanical properties that can not be entirely accounted for by the difference in density. Whether this difference is due to the ancestry of the tree or some other cause, such as soil conditions, is not yet known 7. The strength of small, clear pieces is greatly increased by seasoning. In large timbers, the increased strength attending a loss of moisture is mostly offset by checks and other defects developed during the seasoning process, and therefore, under most conditions it is not considered advisable to anticipate any added strength due to seasoning. METHODS OF TEST The methods of test^ used in obtaining the data in Table 3 are shown in Figs. 3 to 10 inclusive. ^ With each figure is a * For a more detailed description of the methods of test used by the Forest Service see Forest Service Circular 38, "Instructions to Engineers of Tim- ber Tests," revised, Forest Service Bulletin 108, "Tests of Structural Tim- bers, " by McGarvey Cline and A. L. Heim, and a paper presented at the 6th Congress of the International Association for Testing Materials, "Forest Service Investigations of American Woods with Special Reference to In- vestigations of Mechanical Properties, " by McGarvey Cline. * Several methods of testing wood not referred to in Table 3 are given for the sake of completeness. Fia. 3.— Bending test, 8" X 16" X 16' bridge stringer. - BE^^.DING «- Lo t= :3» '"» "'""'"■• k' / / / i« / I. / ,/ 1 / El« CicL mit ^ / 3" / HH / S^^jS"X:3 10 >— / II 0.4. CLS Dcfleetian in Inehe) FiQ. 3a. — Streaa stroia diagram for bending test. Figs. 3 and 3a. — Method of testing large beama in bending and reaulting diagram. THE STRENGTH OF WOOD 17 DESCRIPTION OF FIGS. 3 AND 3a. Specimen. — Contains defects common in material bought on the market. The commercial grade is determined by the number, size, and position of these defects. Bridge stringer, 8" X 16" X 16'. Set Up. — Specimen rests on rocker supports (6), with bearing plates (c) between the supports and the specimen. The suppoits rest on extension arms bolted to the weighing platform (a) of a universal testing machine. Load is applied continuously at the two points (A, h) each one-third length of span from end supports. Load is applied by the machine head at (d) and trans- mitted through the double channel beam (e) and through the roller bearings (^1 h) to the specimen. Speed of machine 0.25 inch per minute. DefonncUion. — Deflections at center are measured by a fine wire (i) kept taut by a spring stretched between two nails driven midway between the top and bottom faces of the specimen vertically above the supports. The wire crosses a steel scale {k) attached to the specimen. The movement of the wire with reference to the scale shows the amount of bending. ReavUa Calculated. — (a) Fiber stress at elastic limit. This is the greatest stress that can occur in a beam loaded with an external load from which it will recover without permanent deflection. (h) Modulus of rupture. This is the greatest computed stress in a beam loaded with a breaking load. (c) Modulus of elasticity. This is a factor computed from the relation between load and deflection within the elastic limit, and represents the stiffness of the wood fiber. •(d) Longitudinal ^hear. This is the stress tending to split the beam length- wise along its neutral plane when under maximum load. (e) Work to maximum load. This is the energy or work required to bend the beam to its deflection at maximum load. It is a measure of a combination of strength and toughness or shock-resisting ability. 18 TIMBER Fig. 4. — Method of testing small beams in bending. Specimen. — Clear, straight^grained, 2" X 2" X 30". Set Up. — 1. I-beam, (/), with two knife-edge supports, (6 b), 28 inches apart, placed on weighing platform of universal testing machine. 2. Specimen rests on knife-edge supports, (6 b) , with roller bearings, (c c) , inter- posed between the supports and the specimen. 3. Load applied continuously at center of span through the bearing block (a) ; speed of machine 0.105 inch per minute. Deformation. — Deflections at center measured by means of special deflecto- meter, {d e). The deflectometer rests upon small nails driven vertically above the knife-edge supports midway between the top and bottom faces of the speci- men. The indicator, (e), is fastened by means of a thin strip of steel to a small nail on the neutral axis midway between the supports. As the beam deflects, the indicator drops by gravity, indicating on the scale, (d) , the amount of deflection to the nearest one-thousandth of an inch. Deflections are observed for every 50 pounds increment of load. Results CcdcuUUed. — (a) Fiber stress at elastic limit. (6) Modulus of rupture. (r) Modulus of elasticity. (d) Work to maximum load. THE STRENGTH OF WOOD -^ lEO iS, SS. 7j i / ' - S 80 1 1 ' Eta .(ic Ua K .d ~ - f - f . s Flo. 5a. — Stress strain diagrain for compTession teet. Fios. 5and5o.— Method of makinR a test in compression parallel lo grain, and reaultina Fig. 5.— ComprcBsion paratlot to grain. Specimen. — Clear, straigli (-grained, 2" X 2" X 8"; ends carefully squared. Set Up. — 1. Yokea, (6 h), placed on specimena inches apart, held in place by thin, pointed aorewa. 2. Specimen rests on ball and socket bearing, (a e) ; load applied continuously; speed o( machine 0.024 inch per minute; care should be taken to have the ends of the apecimen cut smooth and true so that the load is distributed uniformly over the ends. DeformoHon. — Deformation between yokes meas- ured by means of Olsen com prcsso meter. The arms of ths CO mpresso meter are brought in contact with the yokes, (b h}, by means of the spacing bars, (e c). ReauUs Cfdculaled. — (a) Fiber streas at elastic limit. {h) Maximum crushing strength. (c) Modulus of elasticity. Fio. 6. — Compression perpendicular to gnun- COMPRESSION :> ?^ / / /^: but "i Bit j Jj BtHi niS 1 1 r 1 1 1 1 U ^inch). 3. Load applied gradually; speed of machine 0.25 inch per minute. Remlti CaictdaUd. — Maximum load divided by width of specimen in inches. brief description of the method and meaoing of the values de- rived from the tests. In addition to these values moisture de- terminationa and specific gravity determinations are made on each test specimen and the specimen is carefully described. Typical stress-strain diagrams for three kinds of teats — bending, compression parallel to grain, and compression perpendicular to grain — are shown. Method of Deteruinino Moisture Content op Wood 1. Saw a section 1 inch thick from the piece of lumber whose moisture is to be determined. The section should be taken THE STRENGTH OF WOOD 25 at least 12 inches from an end as the wood close to the ends is liable to contain less moisture than the average for the whole stick, due to end drying. 2. Remove spUnters from section and weigh (TT). An accu- racy of 1 per cent, is sufficient. Mark weight on section. 3. Dry section in oven at 100° C. (212° F.) until weight (TTi) is constant. If an oven is not available, the section may be dried on hot steam pipes until it ceases to lose weight. 4. The first weight (TT) minus the dry weight (TFi) represents the weight of water dried out of the wood. Divide this loss by the dry weight and multiply by 100. The j'esult is the moisture content (Af ) of the wood expressed in per cent, of the dry weight. M = w X 100 It 1 Holder .Sharp Bod /Container Water Level ^ Sample -xz ifli Fig. 11. — Method of determining volume by displacement of water. Method op Determining Specific Gravity of Wood Specimens 1. Cut typical samples from specimen containing from 5 to 25 cubic inches. 2. Find volume (V) of sample in cubic centimeters by meas- urements or by displacement method (see below). 3. Dry sample in oven at 212° F. (100° C.) until weight is constant. 4. Find weight (W) of sample in grams. W 5. Divide weight of sample by volume of sample y- = spe- cific gravity.^ 1 This is specific gravity based on volume at test. To find specific gravity based on oven dry volume weigh sample after drying and divide by oven dry volume. This will be larger than specific gravity based on volume with more moisture, since sample shrinks in drying. 26 TIMBER Method op Determining Volume by Displacement op Water (See Fig. 11) Place a container partly filled with water on one pan of a balance scale and bring to balance. Stick the sample whose volume is to be determined on one end of a sharp metal rod. Dip sample in paraffine and place under water in container. Adjust the rod in holder so that the sample is held under water but does not touch container. Balance scales again. The operation of weighing under water should be carried out rapidly so as to prevent absorption of water by the sample. Since a cubic centimeter of water weighs one gram the weight in grams required to balance scales after the sample is submerged is the volume of the sample in cubic centimeters. CHAPTER III EFFECT OF MOISTURE AND OF PRESERVATIVE AND CONDITIONING TREATMENTS ON THE STRENGTH OF WOOD EFFECT OF MOISTURE Moisture exists in wood in two conditions — absorbed in the cell walls, and filling the various open spaces or cavities in the cells. The water in the open spaces, ''free" water, has no effect on the strength. If a piece of green wood is dried, it first loses the free water; and until this is gone and the water in the cell walls begins to grow less the strength remains the same. The reduction of moisture in the cell walls causes an increase in strength. The relation between moisture and bending strength, crushing strength, and stiffness for western hemlock is shown in Fig. 12. It may be seen that above about 30 per cent, moisture there is no change in strength, while if the moisture is reduced below 35 per cent, the strength increases rapidly. The effect of moisture on stiffness is comparatively sUght. Moisture strength diagrams for all the more common structural species have the same general form as that for western hemlock. Fig. 13 shows the relation between moisture and crushing strength for a number of woods. When the cell walls have absorbed all the moisture they can the wood is said to be at the fiber saturation point. If the wood takes up more moisture, the additional moisture will be contained in the form of free water in the cell cavities. The fiber saturation point for various species appears to vary between 20 and 35 per cent, moisture. Figure 14 shows the results of crushing tests on longleaf pine, eastern spruce, and chestnut, including pieces varying from an oven dry to a soaked condition. The oven dry pieces have prac- tically no moisture and had the greatest crushing load. They were also the stiffest as shown by the angle between the hori- zontal compression scale and the line marked "oven dry'* on the diagram. The greater this angle the stiffer is the piece. 27 The kiln dry pieces, with shghtly more moisture than the oven dry pieces, rank next in strength and Btiffness followed by several air dried pieces with increasing moisture and lower strength. Jam I: Mtnrtiin.Perceat.Bsiad.on Drr Walsht Fta. 12. — Effect of varying degrees of moisture upon the dtrength and etiffnesa o! sniBll clear pieces of western hemlock. The pieces that were dried and then allowed to reabsorb moisture in a humid atmosphere and the pieces that were dried and then resoaked were the weakest and least stiif of any. It should be noted in the case of specimens dried so as to cause ■Read scale in 1,000 pounds per equare inch. EFFECT OF MOISTURE ON WOOD 29 an uneven distribution of moisture throughout the cross section that the resulting moisture strength curve will be above the curve for evenly dried specimens, and will be gradually rounded off from the wetteat to the driest condition. Figure 15 shows the strength of case hardened or unevenly dried pieces as compared with pieces dried uniformly throughout their cross section. Thia i s Hoiiturt Fenent BoMd on Dry Weisht Fio. 13. — Relation between the crushing strength in compreBdon parallel to grain, and the moisture content for several woods. condition of uneven dryness will generally be true of structural material. The specimens used in Fig. 15 were somewhat case- hardened, as a result of the surface being more rapidly seasoned than the interior; and on this account the diagram is rounded instead of making a sharper angle at the fiber saturation point. The strength of small, clear pieces of wood when dried from a green to a kiln dry condition is frequently doubled. 30 TIMBER In considering the efifect of moisture on wood, it should be kept in mind that a considerable increase in strength due to drying is generally found only in small pieces. This is due to the difficulty of drying larger pieces through to the center and to the weakening effect of checks which frequently occur in drying. Dach dimension = .01 inch- Total Compression - Inches Fia. 14. — Relation between amount of compression and crushing load in pieces varying from an oven-dry to a soaked condition. (Compression parallel to grain— pieces 1^" X iH" X 5%"). EFFECT OF PRESERVATIVE AND CONDITIONING TREATMENTS Wood-preserving processes may be divided into two classes — superficial processes and impregnation processes. In superficial processes, the liquid preservative is appUed to the wood by a brush or by dipping; in impregnation processes the preservative is forced into the wood under pressure. The wood to be treated EFFECT OF MOISTURE ON WOOD 31 (ties, piling, structural timber, etc.) is placed in large steel cylin- ders; the cylinders are then tightly closed, and the preservative is run in through pipes. When the cylinders are full of preserva- tive, pressure is applied and the preservative is thus forced into the wood. Sometimes it is difficult to force a sufficient amount of preservative into the timber under treatment and in such cases the wood is steamed before treatment to render it more perme- able. BoiUng in the preservative is also practiced. The im- pregnation processes,^ the efifect of which is considered 'here, are those in which steaming and boiling are used. «j 13.000 £12.000 ^11.000 'o ft 10,000 1 9,000 e 1" 8,000 9 2 7,000 (4 6,000 a "a 6.000 \ \ i «. ^^ h.Jt> C HES FNU T \ s k. \ ^ %\ \ \ \ v "^•^ ' •*• ^•"^. \ "'"^- 1 -~ — -m, ,,__ 1 \ ■ Sven l7 D ied ?Iec< 1 1 1 1 i S 1 JO ] 15 i » ! s s 10 I 15 4 10 4 i5 G £ )5 G C ;5 \ 10 ' 75 i » £ i5 \ K) t 4.000 1^ Moliturc Percent of Dry Weight Fig. 15. — Effect of casehardening upon the form of the moisture-strength curve in bending tests. The upper curve is from casehardened specimens, the lower curve from uniformly dried specimens. The preservative generally used is creosote, an oil derived from the distillation of coal tar. Tests on Treated Southern Yellow Pine and Douglas Fir A series of tests was conducted by the Forest Service over a 'period of several years to find the effect of commercial creosote treatments on the strength of southern yellow pine and Douglas fir stringers. To show this efifect a comparison was made be- tween the strength of treated and untreated stringers of the same size and quality. The stringers of both species were 8X16 inches in section and from 28 to 32 feet in length. The sticks were ^ For a full description of the various processes, see ''The Preservation of Structural Timber, " by H. F. Weiss. 32 TIMBER sorted in pairs with the object of having the sticks in each pair as much alike as possible. At the time of treatment each stick was cut into two stringers of equal length, making four test stringers in each group, two butt cuts and two second or top cuts. In order to neutraUze the variation in strength between butt and top cuts the butt ends were treated in one group and the top ends in the next, and so on. Figure 16 shows the method of ctitting the test material. One stringer in each group was treated while green and tested; one was tested green; one was treated, seasoned, and tested; and one was seasoned and tested. In this way the relative strength of the treated and natural material, both green and after seasoning, was shown. Bt lU a Toi 1 Treated •■ Becelved and Teated Immediately Teated aa Becelved 2 Group I I ^ 3 Treated aa Beceived and Seaaoued before Teating Seaaoued before Teating 4 B bU Top 5 Teated aa Beceived Treated ai BeceiTed and Teated Immediately 6 Gxoap U [ 7 Seaaoned before Teating Treated ai Becelred and Seaaoued before Teating 8 ab — Dlak.l"Tbick. Cut from Center to Determine Moiatare Fig. 16. — Method of cutting and marking test material. The southern yellow pine stringers were of two kinds, longleaf pine and loblolly pine. The longleaf pine stringers were high grade timber and the loblolly pine stringers less valuable. The latter contained about 30 per cent, sapwood. The Douglas fir stringers included three grades.^ It is customary to use only timbers of the two higher grades in permanent structures. Two processes of treatment were used with Douglas fir, the "boiling" process and the "steaming" process. Methods of Treatment. — The preservative treatments to which the three species of structural timber were subjected were briefly as follows: ^ Select, Merchantable, and Common as classified by the grading rules of the West Coast Lumber Manufacturers' Association, now the West Coast Lumbermen's Association. EFFECT OF MOISTURE ON WOOD 33 Loblolly Pine.* — Steamed for four hours under 29 pounds pressure ; vacuum of 26 inches applied for one hour; cylinder filled with creosote and pressure of 125 pounds applied for four and one-half hours at a temperature of 140° F. ; vacuum of 23 J^ inches applied for one-fourth hour. Absorption of oil, 13J^ pounds per cubic foot of wood. Longleaf Pine.* — Steamed for six hours at 30 pounds pressure; vacuum of 26 inches applied for one hour; cylinder filled with creosote and pressure of 128 pounds applied for five and one-half hours at a temperature of 140° F. Absorption, 12% pounds per cubic foot of wood. Douglas Fir.* — Boiling process. Boiled in creosote, for twenty-one and three 'fourths hours at temperature of 215° F., loss of moisture during boiling, 1.2 pounds per cubic foot of wood; pressure raised from to 145 pounds per square inch in five and three-fourths hours; temperature about 190° F. Absorption of oil, 11.2 pounds per cubic foot of wood, as determined by measuring tank readings. Douglas Fir. — Steaming Process. Steamed at 90 pounds pressure per square inch for four and one-fourth hours; temperature about 325° F.; vacuum of 20 inches applied for eighteen and one-half hours; temperature 220° F. at end of period; cylinder filled with oil and pressure raised from to maximum pressure of 140 pounds per square inch; pressure period, two and one-fourth hours, temperature of the oil, about 208° F. Absorption, 31 pounds per cubic foot of wood, as figured from increase in original weight of stringers. The stringers were not weighed after steaming, so that the probable loss can not be taken into account in computing the absorption. Methods of Test. — The stringers were tested in bending by supporting them at the ends and applying the load at two points located one-third of the span from each of the end supports. This system corresponds closely to conditions of practice. In testing the beams the load was apphed gradually and a record kept of the deflections corresponding to regular load increments.^ After failure occurred in the stringers, small pieces 2X2 inches in section and 30 inches in length were cut from the unbroken portions. These pieces were selected free from defects and with straight grain. Their location in a cross section of the stringer was noted, so that data could be secured on the relative strength of the inner and outer portions. The tests of small pieces in- cluded bending, compression parallel to grain, ^ compression perpendicular to grain, ^ and shearing.^ Results of Tests. — The results of the tests on the natural and treated stringers are shown in Table 4.* Table 5 gives the ^ Run made March 4, 1908. *Run made March 5, 1908. •For method of test, see Chapter II. ^The tests on Douglas fir treated by the steaming process and seasoned are not yet completed. 34 TIMBER m 1 5 h-sf ■M 9 2 '^ 00 "' S— 0) g fl 4S J « go ^ ft. 5 a « o 0) s ^ s s 00 s. 43 Z Z Z a o • mm d 8 a «8 QQ COOI^ C0Q0 -^l* "t 00 « 1*^ «OUdC0 COOO-^ tOO'^ coxoo ici^ico i^tocsl cocoes ^i-QO 00>Q i0i-«0 »-i»HCO 00C4O C4 ooo*^ OOCOCO COOb* ■ • • • • • OO-^O "-t-^OO coube4 "^^co CtOOO CtOCO CO CO >o 1^ to o ^ ^ CO CO ^ CO -^oo e«400 ^ CO CO 00»^«-t CO"^CO ClOiO • • • «*OI^ co>oc4 OOOO NCOCO C^tOOO >ooo dOO kOOO ooooo C0>OC4 oooco CO ^ CO COMCO ^lOCO ■^ oco CO^ CO lOl^iO ^lOCO 094< co»o( ooo CO • • • CO coo COUdOl o»oco ot^co ococo cocor* -^'iC*H OOOO ICI^'^' l«^C4C0 C40^ C0OC4 ■ • • • • • i-HO>0 1-tOO oo^ • • • "«*0«0 CIOOO MOCO ^I^O OCOI^ 00 cox OOCOt^ OOCO Ot^t^ tOtOO t»MO fi-a EFFECT OF MOISTURE ON WOOD 36 H Q P O » Q t^ OQ ^ ►H QD H a o 0$ 0$ h & OS O £ OQ -< H i4 H O <5 P H Q h4 O < ^ S3 o iz; o OQ H iz: H OS T H 9 O o M g o b S SI S « ftn* J. 1-3 i a 'I 1^ >> d d o •♦» ■-3 d o o OQ CQMO O00C4 ^ CO o cooo «0^ ^h-N OBOCQO coco QQO cococo coo>o lOi^eo 00*^0 «eoo oooo»o "^.^"^ coco^ » » » )(NO0 OOCON ^ ^ CO 00 1* 00 OOCO h>«0iO 00 00 00 Soo OC0»H •k » •• Ol^CO UdOO ^B' ^J* ^^ coco 00 ^lOCO » » • CO CO CO CO coo co^t* oo« OOQOiO i-iOOi a>OiOO r-tv^wt •"•"-•OO C1C>«t* COM^ 00>-i«3 h«C^|Tri oocyte i-HCOt« 0)941^ COCOOO NNN CDCOU) OOO h.iO00 0»0h. »o^o» O900 (NOt* >0.-teo OiOiOi COCO^ »OOJC« i-<'NCO 00>0> OBOOQ ododod NNco co^«o Oiooo t>^oo»>r OOOftt^ SMoo odo COCO'^ C0^C4 '^OitO '^COOO cOO>^ 1-HCOcO OOOJ-* -OiOO^ C0C0«0 h.l^»0 NeO^ COCOM C^COCO oioJ-^ oiood cocO'^ r«h.io o^o> co^N 04 iQOcO XOCO wtw^yft 01 CO c^i COOOOI OOOO dc)04 0404<-) <^C0C0 COOO^ O O) O to' ^ CO C00400 »-H^H fH OJTfiO COt-cO 0404 04f-t 00O4CO CO^iO 0404 0404 OOOO ^t«h« CO^f-i 1OO404 OOiJiTj* COOOtQ 0404 04»H O^cO O^CO C004 C004 00 ■^■^t* Tt*O4 04 CO COCO CO CO CO ||?(§3-^^o3 36 TIMBER results of tests on small pieces cut from the uninjured portions of the stringers after test. Stringers. — The values for modulus of rupture (bending strength) and modulus of elasticity (stiffness) for the natural and treated stringers in each group are compared in Figs. 17, 18, 19, 20, and 21 for loblolly pine, longleaf pine, and Douglas fir. The diagrams were made by first plotting the values for modulus of rupture of the natural beams (solid lines) arranged 10000 9000 8000 7000 (^0000 00 u & 5000 S4000 8000 2000 1000 Tetted Directly after Treatmeat Air Dried and Tested ■ ^-^t^^^ >^^I^^H^ B^^^^^^ ^^^^^^— ^^^^^^ - — — ^— — ^^ J jg ^ - . . . Modalas of Buptare 1000 2000 •2 1800 00 1000 1400 o 1200 1000 ( I / V \ / .\ L. ^ c N * r ... '•-4 '^ ■ Modulai of Elasticity 2000 9 1800 oo & IBOO g 1400 o r.-38 29 30 21 22 26 25 841. 33) > # Nat oral B ^ Batti 8 1200 3 1000 Seam Numbera— r^| JJ ^••O Treated T =• Top* - 1 / "^ i — i > < r--' >-- ■< )..-< r-^ ) Modalos of Klaiticity 31 32 23 24 36 35 28 --Y. 27-2'. Fig. 17. — Effect of preservative treatment on the strength and stiffness of loblolly-pine stringers treated partially air dry. from the highest to the lowest, beginning with the highest value on the left. The modulus of rupture of the treated half of the test pieces (dotted lines) was then plotted on the same ver- tical line as the untreated pieces. The modulus of rupture values for the natural beams are marked (B) or (T) to show whether they are butts or tops. The values for modulus of elasticity for the same beams are plotted in the lower part of the diagrams. All values for the same beam are in the same vertical line. EFFECT OF MOISTURE ON WOOD 37 Loblolly Pine. — Figure 17 shows that when the butts were treated the breaking strength of the butts and tops of the loblolly pine stringers fell rather close together, while when the tops were treated the breaking strength values were much farther apart. This shows a weakening due to the treatment even con- sidering the lower breaking strength of the top stringers. The tests are too few to form a basis for definite conclusions. The Tested Directly after Treatment Air Dried and Tested 10000 9000 8000 1000 6000 00 » 5000 d 4000 3000 2000 1000 JktB- Modalos of Buptare lOOOO 9000 8000 7000 d *^6000 OD I 5000 ■ 1 4000 3000 aooo 1000 { "n > ^'s / 1 > T VN-- T < < N / T s \t Modalai of Baptare 2000 -I 1800 or 00 % 1600 \ 1400 e At _ 1200 1000 . \ 1 \ k / 4 J / / \ L C 5 2000 Modalas of Elasticity jsr.-i3 2 18 10 5 r.-i4 1 .17 9 P •— •Kataral S s Butts ]- 1000 Beam Nambers — { 15 16 8 O— O Treated T ■» Tops Modalas of Elasticity Fig. 18. — Effect of preservative treatment on the strength and stififness of longleaf-pine stringers treated partially air dry. amount of weakening due to the treatment was probably not above 17 per cent. The stififness shows a greater weakening due to treatment than does the breaking strength. Both treated and untreated stringers showed a strength about 30 per cent, greater in the seasoned material than in the material tested directly after treatment. Longleaf Pine. — Figure 18 shows that the breaking strength of the longleaf pine stringers was apparently unafifected by the 38 TIMBER treatment used. There was a slight reduction in the stiffness. In the air seasoned beams the untreated butt cuts were higher in strength and stiffness than the treated top cuts; but on the other hand, the untreated top cuts fell below the treated butts in strength and stiffness in nearly every case. In the stringers tested immediately after treatment, there is less variation between the treated and untreated material. Douglas Fir. — Figures 19 and 20 indicate a marked weakening in the breaking strength of the Douglas fir stringers treated by the so-called "boiling " process as used in this case. The average 10000 9000 8000 o 7000 « 6000 5000 4000 3000 2000 1000 B 2000 S 1800 • 1 ■D « T Ji \ D B T B ■ r» r» ( L- ^-., i \ " '. " . ?" T B B T -D— ^■"•\ \ / / '---( y ^, K > JO ,jr- ^ T } \ > * « * ,,'« .-■' f \ f y.U >•-.„ k- r' '"•'•< ^•'•y Modulas of Baptaro % 1600 ^ 1400 { n , K X i ( \ r'"" \ * n h N — J # % % ■*« — 1 i N • L 'j 1 Ksaal \ A L ) t^ T ^ ^ 1 i ■ \ J A ••-^ ^ / \ ?^ 1 ^odalas of JElMticity 012 3 4 5 C 7 8 9 10 111213 14 1516,17 18 19 20 * BMm Number 1200 1000 »N»taral ^.-O Treated CBoiling Proceii) B ■» Batts T—Tope Fig. 19. — Effect of "boiling process" of preservative treatment on the strength and stifiFness of Douglas-fir stringers treated green and tested without seasoning. breaking strength of the treated stringers tested green and after seasoning is 33 per cent, and 39 per cent., respectively, less than the average strength of the natural stringers. In the green ma- terial no weakening is apparent in the stififness. The seasoned stringers, however, show a falling off in stiffnegs in the treated material. Figure 21 shows the strength and stiffness of green Douglas fir treated by the so-called "steaming" process and similar natural stringers. The breaking strength was considerably EFFECT OF MOISTURE ON WOOD 39 00 less in the treated material (35 per cent.), and the stiffness was slightly less. Small Pieces Cut from Stringers. — Table 5 shows that the sticks cut from the treated loblolly and longleaf pine stringers are in general weaker than those cut from the natural stringers, but the difference is slight except for partially air dry loblolly pine. Part of the apparent loss in strength of the treated mate- rial may be ascribed to its higher moisture content indicated by determinations for moisture in various parts of the cross sections of the treated timbers of these two species. 10000 9000 8000 7000 6000 5000 o 4000 3000 2000 < K^ \ T> ^ L B B ^ T- T- ? : " s r T T T— Ld "^ i> T T B i— B < X \ \ # ^. / > -/ v... )-'- )— < J y"' > \ \ \ * 9 't y' 1 y ^ --i ^•IIKI^ 1 ^••. >-— < > { >•— < i \ ) Modalai of Buptara eo 9 ■ o Modulo • of BUstlcIty 8 9 10 U 12 13 14 13 Id 17 18 19 Beam Number 'Natural O—O Treated ( BolUog Proceti ) B — Bottt T ■> Tops Fig. 20. — Effect of *' boiling process" of preservative treatment on the strength and stiffness of Douglas-fir stringers treated green, air seasoned and tested. In the Douglas fir treated by the boiUng process and tested green, the average (Table 5) for the outside sticks shows a decrease in strength over the natural, with but little difference in stiffness. As compared with the natural sticks, the treated sticks cut from the interior of the main beams showed a more marked drop in strength and stiffness. The air dry material in all cases showed a decided decrease in the strength of the treated sticks. The decrease in stiffness was less marked. Part of this decrease may be accounted for by the higher moisture content of the treated pieces. 40 TIMBER Special Tests on Small Pieces. — Table 6 gives a condensed summary of the results of a series of tests on small clear speci- mens (2 by 2 inches in section) of Douglas fir, longleaf pine, and shortleaf pine made to study the effect of the various steps used in the treatment of the full sized stringers. Eight sticks were subjected to each of the processes shown in Table 6. One- half of the sticks were tested shortly after treatment and one- 10000 9000 aooo a 'TOOO ■ ■ 6000 6000 £ 4000 8000 MOO 1000 t T i i 1 •—^ ^ ^ B B , ^T B ^ B { \ s * ^•-, > B ^T ^4.1 \ • S A y \ ^..-< y \ ,0 Treated (Steaming Proceii) B = Butts T — Tops Fig. 21. — Effect of "steaming process" of preservative treatment on the strength and stiffness of Douglas-fir stringers treated green and tested without seasoning. half after they had been piled in the laboratory long enough (5 months) to reach a practically constant weight. All the processes caused a reduction in the strength values of the unseasoned material of the three species with, in most cases, a recovery after seasoning, except in the tension tests. In these the weakening in the unseasoned material remained after season- ing in all processes but the creosote bath (next to last column). The shrinkage measurements on the steamed material, with i 1 1 J FECT OF MOISTURE ON WOOD SSS SS| SS| 2S| SS5 ESS S-^" 41 2 1 s i II sss sss S!s ass sss »== I 4 a ■41 8 il § ;8 I ;| 5 :: S :S ; : ; ' :5 1 a 1 11 11 r la 31 : : ; S5S 1 i^ 11 « S is 1 :| S :s S ;§ S :e i i i - i» J" 1 11 : ; : S :S : : : i 1 1 51 11 5l : : ; SJ5 11 SSS S$S SeS SfcE !5Sg °== ; : IS f i 1 a ::H::iii|::|::: 42 TIMBER and without vacuum, showed less than 1 per cent, decrease in volume during treatment for all the species. After seasoning, a shrinkage of from 8.4 per cent, for Douglas fir to 10.6 per cent, for longleaf pine was recorded. Steaming and vacuum followed by creosoting showed a somewhat higher shrinkage for Douglas fir than for the pines, both in the unseasoned and air dry pieces. The creosote bath had little influence on the shrinkage, the re- duction after seasoning corresponding closely to the shrinkage of untreated pieces. The pressure treatment following the creo- sote bath showed a somewhat higher shrinkage for Douglas fir than for longleaf or shortleaf pine. While the series of special tests does not explain the weakening in the Douglas fir stringers, it indicates that the trouble has to do with stresses in the full sized stringers, probably caused by rapid and unequal shrinkage during the process. Deductions. — 1. Timber may be very materially weakened by preservative processes. 2. Creosote in itself does not appear to weaken timber. 3. A preservative process which will seriously injure one timber may have little or no effect on the strength of anorther. 4. A comparison of the effect of a preservative process on the strength of different species should not be made, unless it is the common or best adapted process for all the species compared. 5. The same treatment given to a timber of a particular species may have a different effect upon different pieces of that species, depending upon the form of the timber used, its size, and its condition when treated. CHAPTER IV STRENGTH OF WOODEN PRODUCTS Structural Timbers — Strength of the Principal Struc- tural Species — Characteristics Affecting the Strength OF Timbers — Characteristics Affecting Decay in Timbers — Relations Indicated by Tests — ^The Grad- ing OP Structural Timbers — Classification of Defects — ^Examples of Commercial Specifications AND Grading Rules for Structural Timbers — Working Stresses — Telephone Poles — Cross Arms — Packing Boxes — Compression and Drop Tests — Tests by a Revolving Drum Machine — Wooden Vehicle Parts — Spokes — Shafts — Axles — ^Poles — De- ductions FROM Tests The value of certain qualities in wood depends on the use to which the wood is put. Properties which are absolutely es- sential for one use may be of no particular importance for another. Tests on wooden products serve to show not only the suitability of different species for certain uses but also the strongest forms of the product. The following tests on structural timbers, telegraph poles, cross arms, packing boxes, and vehicle parts were made to com- pare proposed substitutes with material considered standard or to determine the possibility of improving standard forms so as to obtain a more satisfactory product with the same or a smaller amount of material. In all tests of this kind the con- ditions met with in commercial use were duphcated as nearly as possible. STRUCTURAL TIMBERS Strength of the Principal Structural Species Tests on the strength of structural timbers furnish the basis (1) for determining the proper working stresses and factors of safety to use in the design of timber structures, (2) for studying 43 •3 1 flip is ig :g ;i :| :i S ;S 1 il s 1* iS 1 ; ;i 1 i sg ; ; sm i f IK i| II 1 11 I II 1 II ^ a ' f i ;| m :§ 11 M p i.s. 11 1 ^ i r4 iS il ;i is m IS 11 SI -- «oS -rf «V e=f «fl- n« *e 'I fi ill :| II :S 11 II 11 16 II li ;S S : :g " : S2 2 : S5 2 ; m is s : is s ; ss a ; § i a i ■ 1 1 pplllflll STRENGTH OF WOODEN PRODUCTS 1 m ;| i ;s i :; i jF lill 51 i ; 5 ; 1 : 1 ; ;§ aP II 11 11 II II ;| 1 m 11 ii !■! 11 i- P m lE §1 B li II 11 li II ii i! is II 11 I! 5:5:=i:ii:5 Bill fill f 3 t||l_ 46 TIMBER the relation of the physical characteristics and defects of timber to its strength, and (3) for preparing grading rules and specifica- tions for various forms of structural timbers. Table 7 shows average strength values for a number of the principal structural species.^ The averages for the bending tests are the results of tests on unseasoned timbers ranging from 4X10 inches to 8X16 inches in cross section for the structural sizes, and of tests on small (2"X2"X30") specimens (cut from large beams after test) free from defects. Many publications dealing with timber give results of tests made only on small, clear, seasoned specimens. Such values may be from one and one-half to two times as high as similar values from tests on large timbers and joists containing the ordinary defects. In applying to commercial material values derived from tests care should be taken to see that the com- mercial timber is of the same quality as the test timber or that the proper adjustments are made in the test values so that they may accurately represent the material in question. The two qualities of greatest value in the wood of structural timber are strength and durability. In order properly to select material for a given use, a knowledge of the influence which the visible characteristics of timber have on these two qualities is necessary. Characteristics Affecting the Strength of Timber The characteristics to be considered in judging the strength of timber are density of wood, direction of grain, rate of growth, moisture condition, proportion of sapwood, size and condition of defects, such as knots, checks, and shakes, and the position of the pith in the cross section. Density. — The strength, hardness, shock-resisting ability and stiflFness of wood vary with its weight when the wood is in the form of small, clear, straight-grained pieces of the same moisture content. The relation of bending strength to dry weight for a single species (longleaf pine) is shown in Fig. 22. In this figure each point represents a single test, the location of the point being determined by the bending strength (modulus of rupture) and * For a more complete discussion see Forest Service BuLletin 108, "Tests of Structural Timbers." STRENGTH OF WOODEN PRODUCTS 47 the dry weight (specific gravity) of the piece tested. The greater strength of the heavier pieces is evident. The relation of bending strength to dry weight for 1 13 different species is shown in Fig. 23. In this figure each small circle represents an average of about 60 tests made on five typical trees cut in one locality. The circles are located according to the average bending strength (modulus of rupture) and the average specific gravity of each group of tests. The solid circles I.. Spwille Gravitr Fia. 22. — Relation between beDding strength &nd dry wei|[ht for longleni are for green material and the open circles for air dry material. The numbers show the species and locality of growth. For ex- ample, the solid circle 3 shows the bending strength of green Eng- elmann spruce cut in San Miguel County, Colorado, and the open circle 3 shows the bending strength of air dry pieces cut from the same trees. Figure 23 shows that the heavier species tested had the greater average bending strength. From Figs. 22 and 23 it ia evident that as the weight increases the strength increases both in the caae of pieces all cut from the same kind of wood and in the case of average values of many different kinds of wood. Fig. 24. — Douglas fir (magnified 50 times). wood; C, Hoaual ring — hub year's growth. Note Bummerwood. In order to make use of this fact in grading timber, some way of estimating density from a visual inspection is necessary. STRENGTH OF WOODEN PRODUCTS 49 The character of the annual rings as shown on a cross section of the ends of a stick of timber furnishes a means of judging ite strength. Wood is made up of concentric rings of growth. Each ring consists of two parts, springwood and summerwood. The springwoodj as its name indicates, is formed first, and in the woods commonly used for structural purposes is the lighter- colored, softer part of the ring. The summerwood is built up later and is darker and denser (see Fig. 24). In certain wooi^ the change from springwood to summerwood is distinctly marked, BO that the proportion of summerwood in an annual ring or in a cross section can be closely estimated. Figure 25 shows the well- defined bands of summerwood and springwood in the ends of two loblolly pine beams. Summerwood is considerably heavier 60 TIMBER than springwood. A number of tests on small pieces of summer- wood and springwood cut from wide-ringed loblolly pine showed a density and strength about twice as great in the summerwood as in the springwood. The proportion of summerwood in a cross section of a stick is therefore a means of estimating its density and strength. It should be remembered that density is the basic factor governing strength and that proportion of summerwood as a satisfactory indicator of strength is dependent on the dif- ference in density of the two parts of the annual ring and on the closeness with which these parts can be differentiated. Rate of Growth. — The rate of growth is generally spoken of in rings per inch. The average rate of growth is determined by counting the annual rings on a radial line on the cross section and dividing the number of rings by the length of the line in inches. In the case of some of the species tested it appears that there is a rate of growth which is generally associated with the greatest density and greatest strength. For a number of the species tested this is: Rings per inch Douglas fir 24 Shortleaf pine 12 Loblolly pine 6 Western larch 18 Western hemlock 14 Tamarack 20 Norway pine 18 Redwood 30 Longleaf pine 10 However, density is the basic requisite for strength, and too much importance should not be given to the rates of growth as an indication of satisfactory material. Abnormal rates of growth, either fast or slow, in structural timbers are frequently associated with material of low density, and timber with such growth should be regarded with suspicion. Very fast-grown wide-ringed timber is also comparatively diffi- cult to work and frequently wears irregularly. The use of nails, spikes, and screws in wide-ringed timber may give trouble on account of the width of the alternate hard and soft bands in each annual ring. Direction of Grain. — By grain is often meant the lines formed by cutting the rings of annual growth. If a stick is cut from a log in such a way that these lines rim diagonally from one edge STRENGTH OF WOODEN PRODUCTS 51 of the stick to the other instead of parallel to the edges, the load that it will carry as a beam will be considerably reduced, and, moreover, failure will be more complete when it occurs. There is, however, another kind of cross grain, known as spiral grain, which is more difficult to detect than that just described, but which also weakens the timber and may cause unexpected complete failure; that is, a break in which the stick snaps in pieces. The wood of the conifers may be considered as built up mainly of elon- gated celb running lengthwise with the trunk, with a much smaller proportion of cells in small bundles located at right angles to them and lying radially. These small bundles of cells are termed pith rays. They are formed much as if a knife blade had been thrust radially into the tree crowding between the vertical cells. Figure 26 shows a magnified piece of wood with the vertical cells and pith rays. The cross sections of the pith rays appear on a magnified tangential or flat-grained face of timber as figures tapering on each end, with the long axis vertical, and on a radial section as light-colored bands. In oak, for example, the pith rays are very much in evidence, and form the figures in quartered material. In the conifers, however, the pith rays are not gener- 52 TIMBER ally noticeable. Not infrequently the cells of which a tree is built up follow a spiral course around the pith instead of lying vertically. Figure 27 shows a tree of this kind. In such trees the cross sections of the pith rays are also inclined or lie diagonally instead of vertically and form an indication of spiral grain. It is quite possible for a piece to be straight-grained, so far as the annual rings are concerned, and still to have a spiral grain. Spiral grain is often indicated in seasoned material by the dif^onal di- rection of fine surface checks which occur at the pith rays. In Fig. 28 are shown three views of a piece of spruce with spiraJ grain. The danger of using such material where strength is necessary is evi- dent. Failure due to spiral grain in a bridge stringer is shown in Fig. 29. Splitting a block of wood radially will show whether or not it has spiral grain. Diagonal grain or spiral grain with an inclination of more than 1 in 20 to the edge of a beam is apt to cause failure and should not be allowed in high-grade material. Moisture. — The effect of moisture on strength is very marked in small Fio. 27.— Trae with spiral grain, clear pieces of wood. In Fig. 23 the strength of the green material averages about three-quarters that of the air-dry material, and small kiln dry pieces are frequently over twice as strong as similar green ones. In large pieces, however, the effect of moisture is much less. Under present methods of season- ing structural material, any increase in the strength of the wood fiber is frequently offset by the weakening effect of checks and shakes induced in the process, so that the strength of large seasoned beams is, on the average, increased little over that of green beams. In Table 8, values for green and air-seasoned ma- terial for a number of species are compared. The green material in each case is taken as having a value of 1.00 and the corre- sponding value for the air-seasoned material is given. The tests were made by dividing the shipments of each species into two parts, one of which was tested green and the other after STRENGTH OF WOODEN PRODUCTS Fio. 28. — Spiral groin id Sitka spraM. Ro. 29. — Failure due to spiral grain. Views of side and bottom of central portion of 8" X 16" X IS' stringer after test. It will b« noted that the lines of fulure do not follow the visible psin (linea formed by cutting the annual rings). |! S 5 !l II m Iflii a.| « i H i M i TIMBER ;3 ;s ;= ;s ;!= ;a ;« ;s ;j 3 ; 2 : SS3 5 : « ; : : S : Sg J : « : «« ^ : ^ : : : ^ : ^o ES S : ; : 8 : t : 3= : : S : S : 33 R£ SS 2^ Sg Kg 2S S3 S : 22 S : : ; t ; S : Sg : : S : l:;S:2:5;S:S:S: :;S -! " S ~i !: 15 2: Sa 8S 26 23 22 SS «S! S2 I SS 2S 3& 3S 2S SS SS SS SS liii • STRENGTH OF WOODEN PRODUCTS 55 thorough air seaeoning. While the results show that, in general, all of the mechanical properties are increased by seasoning, this increase is irregular in the structural sizes. In the small sizes an increase in strength would of course be expected. It has been found-that if the moisture content of a seasoned timber is increased it loses strength and that if it is thoroughly soaked with FlO. 30. — CrOBB se«tiOD at looEleaf-pine tree shawine Eapwoud and lioartwood. water it will be weaker than when green. It is hardly safe in designing timber structures to depend upon an increase in strength in timbers due to seasoning. Sapwood. — The sapwood forme the layer between the bark and the heartwood. Sapwood is generaUy considerably lighter in color than the heartwood in the species commonly used for structural purposes. Figure 30 shows the heartwood and sapwood in a cross section of loi^eaf pine. As a tree grows, the sapwood 56 TIMBER is continually changing into heartwood and new sapwood is constantly being added at the circumference. All of the heart- wood in a mature tree was at one time sapwood. The propor- tion of sapwood as such has no bearing on the strength of a stick of timber. If a tree is cut at a time when it is forming its densest wood so that this dense wood is still sapwood^ pieces cut from the sapwood will be the stronger. K, on the other hand, it is cut later in life when the wood being formed as sapwood is not so dense and the denser wood has changed to heartwood, then pieces cut from the heartwood will be the stronger. In mature coniferous trees the sapwood is generally weaker than the heartwood. i TOP VIEW VoU 3 VoL2 Vols I QQ VoL 1 - L- VoL 8 SIDE VIEW I A A P FiQ. 31. — Division of beam into volumes for location of knots. Measure- ment of knots on horizontal and vertical face of beam, d » diameter of knot. Defects. — Knots, checks, and shakes are the most common defects affecting strength. In timber for use as beams, the in- jBuence of knots on strength is largely a matter of location. Figure 31 shows a method of dividing a beam into three volumes with reference to the location of knots. Numerous tests have shown that knots occurring in Volume 1, which occupies the lower quarter of the central half of the beam, have considerably more weakening effect than similar knots occurring in other volumes. Loose or rotten knots are of course more harmful than those closely knit with the surrounding wood. A comparatively small knot situated near enough to the lower edge of a beam to turn the grain off is more harmful than a larger knot so placed as to allow the grain to be continuous in passing. In some cases knots near the neutral plane (the horizontal plane passing through the STRENGTH OF WOODEN PRODUCTS 67 center of a beam) may act as pins and tend to strengthen the beam against failure in horizontal shear or splitting from end to end along the center. Figure 32 is a view of a beam that has failed in horizontal shear. In a series of testa' on loblolly pine beams those with knots in Volume 1 had about 75 per cent, of the strength of sticks with knots in the remaining portions. Tests on short columns^ of Douglas fir, western hemlock, and Fio. 32. — View of beam at completion of test showing failure in horiioatal shear. Note that beam has split along center so that top half projects above lower half at end. AA, support for beam on weiglung platform. BB, points where load ia applied. C, head of screw press. D, straining beam. EE, fine wire stretched along center of beam. F, scale used with wire for measuring deflection of beam under load. western larch indicate that the crushing strength of material witii knot^ is less than that of clear material. The decrease in strength was approximately 5 per cent, in columns with knots J^ inch or less in diameter, from 10 to 15 per cent, in columns with knots between }-i inch and 1^^ inches in diameter, and from 15 to 20 per cent, in columns with knots over 1^^ inches in diameter. Checks are caused by the stresses set up in seasoning. Struc- tural timber in large sizes is difficult to season without more or •See Forest Service CirealaT 164, "Properties and Uses of Southern ' See Forest Service BvUelin 108, " Teste of Structural Timbers," 58 TIMBER less checking; even under favorable conditions; frequently it is so exposed as to cause the surface to dry much more rapidly than moisture can be transmitted from the inner portions to the surface. The outer portions dry and shrink while the center is still wet, and checking results. A shake is a separation between two annual rings. Generally the separation occurs in only part of the ring, but sometimes it is complete. Shakes are ascribed to the bending action of wind on the standing tree. They are frequently not' visible in greqn timber, but show up later during seasoning. Both checks and shakes weaken beams in their ability to resist horizontal shear in proportion as they affect the area of the beam near the neutral axis. When a load is placed on a beam supported at the ends, the beam has a tendency to shear or split lengthwise along the center of the vertical side and form two beams, each one-half the size of the original beam. If the beani is already partially separated along the center by checks and shakes, it is obvious that it will be more easily split along this plane than if the area is intact. In the case of a stringer, 8 X 16 inches in section, tested in bending over a 15-foot span, failure may occur by tension or tear- ing apart of the fibers in the lower part of the beam, by compres- sion or crushing in the upper part, or by shearing along the neutral axis. The results of shearing tests on small, clear pieces show that, under the conditions given, failure would always occur in tension or compression long before the beam could reach its maximum shearing stress, provided the shear-resisting area was intact. In tests on commercial material, however, horizontal shear is a common form of failure, which is due to the fact that the area that resists shear is frequently weakened by checks and shakes. A comparison of the stresses obtained from tests on 8-inch by 16-inch by 16-foot stringers and from those in small clear pieces shows that the shear-resisting area in commercial material is frequently reduced about 50 per cent, by checks and shakes. Table 9 shows the calculated shearing stresses developed in structural beams of a number of species. Table 9 separates the timbers tested into three groups: (1) Those which failed first in horizontal shear, (2) those which had secondary failures in horizontal shear, and (3) those which did not fail in horizontal shear. The number of specimens falling into each group is given as a percentage of the total number STRENGTH OF WOODEN PRODUCTS 59 OQ » O a a OS OQ CQ O ;? i-i Q < P < 05 a O hi ki ** •«-< at (4 « ft? ki X- a o 3 .£3 hi Q »^ ftl 08 08 S OQ — ft an « a •m ti c hi U a« .ftS "< 08 ft OL I S3 •1 ID hi •§1.^1 C8 rt is QQ — > OJ3 5 08 •<'a * s =^ Ph « ° o u o «_5 jj 00 ,, « ftg^ ^ T»< T»< to »0 O «05 thxoco -ooq oa)oOi-HOOoot»o NCI i-H Ni-t N iH ■^ O <>* OS t>» -00 t- N «e Tj* CO o> o •t* CS| N CO CC 0* CJ CO -(N CDCDCOtoOOCOCOOO 2«0 CS| 00 »0 I-H 00 C^ CI CO CO « CO <© 00 O CO C0»-HC0CJC0CIC1C0CI z CI t>«. « t>» O lO t>. o o»^coci»oos-^cio a hi t>.i-HOOCIi-tOO>00 0» »-HO»'^«O^C0C0CI'^t< s 2J3 s ft^*^, o 2* a >»8 c3 JE=I 60 TIMBER of specimens tested. It will be noticed that of the seasoned timbers from 6 to 56 per cent, failed first in shear, and that in Douglas fir, loblolly pine, and western hemlock a considerable proportion had secondary failures in horizontal shear. These figures indicate strongly the need of taking horizontal shear into con- sideration in the design of timbers tructures. They also show the necessity of using stresses much lower than those indicated by tests on small clear specimens. In short, deep beams special attention should be given to horizontal shear. Position of Pith in Cross Section. — Timbers containing the pith or center of the tree are frequently spoken of as " boxheart. " When the timber was tested in bending, failure occurred more l-ntb not in CniH^tetigii Rinsi Vertieal a - Pttb wJthln Caaur Halt diameter) B Via. 43. — ClassiScatiou of knots according to form (A) and siie (fi). Size { Standard A pin knot is a sound knot not over H inch in avenge diameter. A standard knot ia a sound knot over J^ inch but not over Ij^ inches ii average diameter. Fio, 44. — CroBs St n of timber showing several kinds of detecta. A large knot is a sound knot more than 1^^ inches in average diameter. A round knot is one which is oval or circular in form. A spike knot is one sawn in a lengthwise direction. A sound knot is one solid across its fa«e and aa hard as the wood it is in. It ia so fixed in the piece as to retain its position. A loose knot ia one not firmly held in place. An encased knot is one Burrounded wholly or in part by bark or pitch and not intergrown with the adjacent wood. A rott«n knot is one not aa hard as the surrounding wood. STRENGTH OF WOODEN PRODUCTS 77 A pith knot is a sound knot with a pith hole not over J ndtokded 6 feet from but end. M B™W r. Coto. ■Dd yea de. WMh 19! Rings " ^ Bendiuc gtrenittb stiff .e„ Weiiht Approii- Rstio Ratio te»t^ 'u™ ■ge n ? See load at Modulut oedar BtifT-' to cedar ■ rupture (Idaho) (0;.., factor '■^' Po-«nl lb. *? Ytar, J ,j 21s 222 18 2 060 11.785 a.7 259 30 8 104 22 1 9 8 1 S 2 65 a|470 5^090 12.930 7:880 ii2 8:a 248 34 8 5 144 39 3 29 1 050 7 301 fl 8 10!5IO 5^481 i 2 i laiaso 7.480 8:7 2S0 97 2.2E0 2 4 fl 3 '74 32 46 2 352 i5!a£0 6^070 0^9 1 7 112 23 2180 3.3 304 0,7f.8 iia 2 2 5 1 890 •"■-oo 7,610 3 J30 00 4080 100 a,038 0.3 325 8 S 11 00 8.230 H 2 i" S 24 S t 3 2 10 5.020 ioo ti ioi 440 7 8 i 2B : Ji 74 4;720 51 li 46 203 4 S 7 8 8 lo t 504 4 27 ici Ills in 71 300 ro 10;290 323 1 0,680 7:6 4 7 ■ 5 1 4,7 320 7 74 10 »62 inio sloio 3.420 3;o 3S3 a 5 97 24 572 5.597 'si 0:34 92 3 140 n^iao 101 ro8 I5;s69 4;072 980 4 171 6.610 7.56 287 20 3.60 12 S 800 153 esa 2 9 81 18 ( ISl SfllSBO 10;i90 13:3' 321 S 1 57 0.040 7.41 Ghodf 12 — Deul fr ore of La shipped t 1: Mrio attle .':.>!;:." rn^^e^iS^i^ 'a tUi^^."^^. !1' Df large k rr.nd^"!r arly apid large kno ta a nd judged to be able Romp quit. 00th othera v ry I ough. e butt ths 11 thani "cr "Ifpi 'cTupB 10 an 10 and 12, the V2. '^.T^ n the varioua aroupe withou 92 TIMBER block at a point corresponding to the ground line. The condi- tions of the test correspond rather closely to conditions of actual use where the pole is set in the ground and has to meet stresses applied by the wind to the pole through the wires and cross- arms. Table 12 gives the results of the tests on poles. The stiffness factor is simply a factor which will enable a comparison of the stiffness of poles tested in this particular way. It can not be used to compare the stiffness of poles in other ways. The tests on poles showed the following: Airnseasoned lodgepole pine poles cut from live timber in Monta^na were fully equal in strength to the western red cedar poled tested. In actual stress developed they were superior; but on account of the greater taper of the cedar poles this advan- tage was lost in a comparison based on equal top diameters, the dimension usually specified. Western red cedar poles were superior in maximum load de- veloped to the pine and spruce poles cut from a fire-killed area in Colorado. The fire-killed pine, after standing ten years, did not show de- terioration to any appreciable extent when compared to seasoned lodgepole pine cut from representative live trees in Wyoming and Colorado.^ The advantage in strength of the material from the lodgepole pine poles from Montana can be accounted for by the fact that it was above normal in weight. The two shipments of western red cedar from Idaho and the shipment from Washington were practically equal in strength. The shipment from Oregon was slightly weaker. Northern white cedar poles ranked below any others tested, both in strength and stiffness. The quality of these poles how- ever was noticeably poor. Douglas fir and western hemlock poles were especially strong and stiff. These poles were much heavier than the western red cedar poles. The fire-killed lodgepole pine poles from California ranked between the other two shipments of California lodgepole pine poles in strength. Conditions of growth in lodgepole pine apparently have more influence on the strength than five years standing after being fire killed. ^ From tests on small, clear pieces not shown in Table 12. STRENGTH OF WOODEN PRODUCTS 93 CROSS-ARMS Cross-arms must resist forces which are variable in amount and direction. In a telephone line the arms may be subjected to heavy loads under several conditions: 1. If the wires on one side of a pole are broken, a heavy side pull comes on the cross-arms from the other side. This causes a severe stress in the pole, and, as will be shown later, the pole is more likely to be broken than the cross-arm. 2. If the wires are heavily covered with sleet and there is a strong wind blowing, there is a pressure on the cross-arms; but here again the stress in the pole will cause it to fail before the cross-arm will give way. Similarly, in changes of direction in the Une the sidewise pull of the wires is more severe on the poles than on the arms. 3. If the cross-arms are at the same level in the line, they receive no greater strains than those which may be imposed by the weight of the wires and adhering ice and by wind pressure. If, however, the middle pole of three is higher than the poles on either side and the wires are tightly stretched, there is a strong downward pull on the cross-arm. A similar condition might result if a single pole were left standing in a line where the poles on either side had fallen. A test was devised by the Forest Service^ in which the load was distributed along the arm, as it is in actual practice. The load was applied vertically because the arms are likely to receive their heaviest loads in this direction and because from these re- sults it is possible to estimate the resistance of the arms to forces acting in other directions. The material tested consisted of 84 six-pin cross-arms 33^ by 4J^ inches by 6 feet. These were of four species: Douglas fir, shortleaf pine, longleaf pine, and southern white cedar. The longleaf pine arms were separated into three groups accord- ing to proportion of heart wood. The arrangement of the test apparatus is shown in Fig. 46. The stub pole "/" restson ashort beam on two posts, which in turn rest on the weighing platform. The pole is held in a vertical position by the columns of the testing machine. A gain about 1 inch deep is cut in the side of the pole, and the cross- ^ See Forest Service Circular 204, "Strength Tests of Cross-arms," by T. R. C. Wilson. > 94 TIMBER arm is fastened into it by a ^-inch bolt which extends through the pole. The load is appUed to the cross-arm by rods passing through the pinholes in the arm. Nuts on these rods pull down on wooden bearing blocks shaped to fit the upper side of the arm. The lower ends of these rods are attached to a system of equalizing levers (c, d, and e) whose arrangement is such that the rods transmit equal loads to the cross-arms. FiQ. 46. — Method of testing cross-arms. Blocks, **A," are each attached to the cross-arm by a nail driven into the center of its end. These blocks are held vertical by the guide rods, "g. " A nail is driven part way into the front edge of each block and in line with the center of the cross-arm. Between these two nails is stretched a fine wire, which is kept taut by a rubber band. The movement of this wire with re- spect to a scale in the center of the arm marks the deflection. STRENGTH OF WOODEN PRODUCTS 95 A 1-inch moisture disk and an 8-inch specimen for test in compression parallel to grain were secured from each arm after the bending test was completed. The average values from the tests are given in Table 13. The load at 3^-inch deflection is an approximate measure of the stiffness. " Work to maximum load" is a measure of the tough- ness. The maximum load is the measure of the strength or ability to withstand a slowly applied load. Since the longleaf pine arms with 75 per cent, of heart were stronger than those with 100 per cent., and those with 50 per cent, were weaker, other factors than the relative amounts of heart- wood and sapwood must have a determining influence on the strength. There was a very considerable difference in the strength of the natural and treated shortleaf pine arms. Just how much of this difference should be attributed to the treatment it was im- possible to determine. Both the strength values and the manner of failure show that white cedar is considerably weaker than the other species. The failure was in nearly all cases by short brash tension. The nu- merous small knots and the large season checks seem to have had little influence on the failures. In many cases the principal failure was at the first pinhole from the center; and in view of this fact, particular attention should be given in grading or selecting arms, to defects near the center or the first pinholes. Knots on the upper side of the arms near these points are especially to be avoided. The average load borne by the southern white cedar cross-arms, the weakest group, was 5,000 pounds, the load being applied vertically. Careful estimate indicates that the resistance of these arms to side pull is at least 4,000 pounds. This is more than sufli- cientj under any conditions of service because it is much greater than the side load that can be sustained by poles. In tests, ^ poles have not withstood an average sid^ pull of much more than 3,000 pounds, and usually have failed at less than 2,000. In the case of sleet or snow, if the ice coating on the wires gives each strand a diameter of 1 inch, a wind pressure of 27 pounds per square foot would be suflicient to break the pole, assuming that the poles have a resistance to side pressure of 2,000 pounds and are 150 feet apart. Even under these extreme conditions, ^ See Telephone Poles, page 88. 96 TIMBER ' o o i^ • d 1 • M a C a • 1-4 1 t* S 1 00 00 < 9 hi Ifc «5 ■ 8c^ a 3 5:^-2 • g 9 O s 2 s 1 « 00 0» ■ oo k 1 «0 1-4 pfi J5 S H-a c a ^^ c3 39 ■S /— N . ^^^ ^^^ '^^ x~» /~^ /»v Is 08'-' c 09 gS8S§S§§S5 'S§S .a »«>oo»o»H«t^ooc o? b^t* >o ^. 00 a »— ' >»• '«■>' d 08 • s ; 2 o o s > -* ' 8 i-i ^'>:^s c "«* oc •k s£ ^^"S ^ ^ -^ ^ »o -«*« ■* ec 1 « i -^ ^^ QC 1 ■^ CO CO « - «o • • CO 1 iH *H 1-4 " 1 »" 1 S-'S 4^ d H |- flS o c ' S a » > > c^ § S s. ULT8 as in l1 • d s c > "«* CO -* «c > O" > >o !• %r "* -«*« »0 If •^ •^ •* OD M u <§.! 00 lO c 00 O) «o 1-< »- C4 ^ CM w 1-< F-l 1-4 »H f 1H iH ^ ^M ABLE : 25 X- 13 *^4 s J 1 i H CO 5 t2 t2 t2 • 08 o . g 2 2 s oi , > OQ s 1 1 1 .1^ .r^ > 1 > as • o Li _fl (^ -4J •♦J -tJ ^m ^•^ •M s •3 ^ 08 OS 3 a • s .g ^ w w tn « ff z a • • \6 -*-» ■1^ »4 M t: 08 OS a> 3 0) ^ o rd o 5 >-• 'i »o ^ S O 0) 13 1 1 CQ ^ u> 1 d d d a c c !^ ^ (C 0. P 1. c L OS 1 •a J; 13 J d d o o GO X OQ 9^ 08 g d d CO X o OD a 8 I a- a 08 a 08 a 0) ■♦a 08 d I 0. 3 "oS > STRENGTH OF WOODEN PRODUCTS 97 the cross-arm would have to resist stresses equivalent to those imposed by a load of only 875 pounds, applied as in the tests, so that even the weakest of the arms tested would have more than sufficient strength to withstand a force which would break the average pole. Where there are abrupt changes of grade in a line, as in the case of one pole being higher than those adjacent on either side, the downward pull on the cross-arm depends on the stress of the wires and their inclination from the horizontal. If six No. 8 wires are stretched to their maximmn strength, assumed to be 60,000 pounds per square inch, they can exert a pull of 7,670 pounds. If a cross-arm on the middle pole had the average strength of southern white cedar, it could not be broken by such a pull unless the pole were at least 45 feet higher than the two at each side, the spans being 150 feet. Such an abrupt change in grade is rare in practice. If the cross-arm were weakened to 60 per cent, of its air-dry strength, which would correspond to a green or water-soaked condition, the arm would not break unless the difference in height were at least 25 feet. All things considered, cross-arms of the species and dimensions tested are strong enough for ordinary use. Their strength is relatively of much more importance when they are longer. The ability of the timber to resist decay, and the. methods of pre- venting its decay are considerations of greater importance than strength in the species and sizes tested. PACKING BOXES Compression and Drop Tests In order to determine the relative ability of three styles of boxes, nailed, wirebound, and dovetailed, to stand rough usage, tests were made^ on three sizes of each, ''small,'' ''medium," and "large." The capacity of the three sizes was, respectively, 6, 12, and 20 one-gallon cans 4X6 inches in cross section and 10 inches long. Each style and size of box was tested in three ways, by endwise compression, by diagonal compression, and by dropping. The results with descriptions of the boxes are given in Table 14. 1 See Forest Service Circular 214 "Tests of Packing Boxes of Various Forms, " by John A. Newlin. 98 TIMBER Endwise Compression. — In the endwise compression tests the box was compressed between two flat surfaces in the direction of its largest dimension. In this test the load which the box will stand depends largely upon the character and thickness of the material of which it is made, and the construction playa a relatively unimportant part. Most of the nailed boxes were Fia. 47. — Method of oouductuiK diagonal compression test constructed with two battens on each end, so that only two • of the vertical faces had a good bearing. Thus the loads were less than these boxes might be expected to carry, judging from the thickness of the material. The wires of the wirebound boxes prevented buckling of the sides to a large extent and caused STRENGTH OP WOODEN PRODUCTS 1 |i 1 J s 1:1 Hi 1 M |S 1 ' 1 1 1 III 1 i3s ■i'-i:'. » « s ., „ 2 5 5 J aiii 5 s 1 1 § 1 s i 1 "" " " 1 i 1 a s! s; .1 si 1 5 i 1 S - i i 1 1 6-i 58 = 22 1 = = : = 5! ^ 5 i 1 i Hill III i -i "i S ■1 i :-2 Pi i \ 1 i i i 1 5 ; ; ; ; " : ; " 2 s § : 1 s i 1 si si I s s -f 1 1 1 1 1 ill Is i Is 1 100 TIMBER these boxes to give results relatively high for the thickness of the material. The actual loads supported by the wirebound boxes, however, were lower than for the dovetailed and for most of the nailed boxes. Diagonal Compression. — In the diagonal compression test illustrated in Fig. 47, the box was compressed along a line con- necting diagonally opposite corners. This test produces stress in every part of the box, and the result of the test is the same re- gardless of which corner receives the load. The test causes failure of the box at its weakest point and thus points out the weak features of its construction. The dovetailed boxes with thick ends and the wirebound boxes withstood about the same loads. The dovetailed boxes with thin ends and the nailed boxes gave much lower values. In shock-resisting ability, as shown by the product of the average load from .0 to the maximum and the amount of distor- tion or crushing, the dovetailed boxes with thin ends gave exceed- ingly low values. Those with thick ends gave much higher values, yet not as high as were given by the nailed boxes other than those with single piece ends. The wirebound boxes show much the highest shock-resisting ability. In stiffness or rigidity the dovetailed boxes were much superior to the others tested. This is shown by the lower values for compression at maximum load. Drop Tests. — In the drop test the box was suspended with its diagonal corners in a vertical line and then allowed to drop 1 foot. Each drop was made 6 inches higher than the preceding one and the test continued until the cans fell from the box. Figure 48 shows the method of conducting drop tests. Two forms of construction gave poor results, the nailed boxes with single piece ends and the dovetailed boxes with thin ends. The wirebound boxes showed great ability to withstand the drop test and were quite far ahead of the nailed boxes in this respect. The dovetailed boxes with thick ends were much infe- rior to the wirebound boxes and somewhat inferior to the nailed boxes with cleated ends. The failure of nailed boxes with single piece ends without cleats shows this to be a very poor construction; 12 out of 18 such boxes subjected to drop or diagonal compression tests had both ends split completely in two. The nails driven into the ends of the boards showed very slight resistance to withdrawal. In the STRENGTH OF WOODEN PRODUCTS 101 case of boxes with cleated ends, failures did not occur in that portion of the box. The chief source of weakness was the with- drawal of the nails holding the top. bottom, and sides to the ends. Fio 48 — Method of conducting drop test. An end made of thinner boards with four cleats of a wood of greater nail-holding power would probably give better results. The tests show that the smgle piece end is a poor form of construc- tion and indicate the necessity of using, for certain parts, a wood that will resist the withdrawal of nails. 102 TIMBER The wirebound boxes tested showed a well-balanced construc- tion. The top, bottom, and sides were held firmly to the ends by the wires and by staples driven in red gum cleats. The strength of the wirebound boxes increased with the thickness of the lumber and the size of the wire. In all of the tests the wires were an important element of strength. The thin end dovetailed boxes showed an unbalanced con- struction, since the joints did not hold. The thick end boxes were much better. In both cases the tongue-and-groove joints were weak features of construction. When the joints in adjacent sides and ends were in the same plane the box was materially weakened. The greater rigidity of these boxes resulted in less damage to the contents when failure occurred. Tests by a Revolving Drum Machine The Machine. — In order to secure a method of testing boxes by which the results could be more easily correlated with the conditions of service and by which the tests could be made in a shorter time, a revolving drum box testing machine was developed. ^ This machine consists of a hexagonal drum 4 feet long (see Fig. 49). Each of the six sides is 3 feet 6 inches long. The drum is mounted on a frame, so that it can be revolved. The inside is hned with steel and provided with fixed internal baffles or hazards which cause the box to slide from side to side of the machine and to fall in different ways on the sides, ends, and corners as the drum is slowly revolved. The speed that gives the best results has been found to be 1% revolutions per minute. The machine in Fig. 49 is adapted only for boxes up to a certain size. Its operation is intended to be similar to the roughest handling which a box should receive in service and to measure ability to stand such usage. The machine does not, of course, measure the resistance of a box to static load, such as it would receive if placed at the bottom of a stack of boxes. The Boxes Tested.^ — A series of tests was made on 185 nailed and 75 wirebound boxes. Part were built to hold two dozen No. 3 cans^ and part to hold two dozen No. 2 cans.^ The species 1 For details of the development of this machine, see ** Proceedings of American Society for Testing Materials — 1916," "The Development of a Box Testing Machine and Some Results of Tests," by J. A. Newlin and T. R. C. Wilson, U. S. Forest Service. 2 These cans are the sizes ordinarily used for tomatoes, peas, etc. STRENGTH OF WOODEN PRODUCTS 103 of wood used in making the boxes included white pine, southern yellow pine, yellow birch, aspen ("popple"), yellow poplar {tulip tree), and red gum. In the nailed boxes the end construction included single piece ends, 2 piece cleated ends, 2 piece ends with corrugated fasteners, Fig. 49. — Box-testing machine. and dovetailed ends. The thickness of the ends was K, Ke. %, and J4 inch- The thickness of the sides,, tops, and bottoms was ^, 5^6, and ^ inch sawed lumber and ^g, J42' K> %2 ^^^ ^6 inch rotary cut veneer. The boxes were nailed with 4, 5, 6, and 7d. cement-coated nails — 4 to 9 nails to the nailing edge. 104 TIMBER The wirebound boxes were bound with No. 16 and No. 15 wires stapled with 14, 18, 20, and 24 staples per wire, and had stapled, nailed, and loose ends. Deductions from Tests, — Nailed Boxes, — The tests showed plainly that the resistance of many of the nailed boxes to rough usage could be greatly increased by proper nailing. The number of nails per naiUng edge proved to have a considerable influence on the resistance of the box. Figure 50 shows the relation of number of nail^ in the boxes to the amount of rough handling required to break the boxes. In Pig. 50 the average number of revolutions of the drum required to cause breakage and loss of contents in boxes with 7 nails per nailing edge is taken as 100. 100 I SH120 «- 80 • 1 / > n / < / Mg 20 < n 12 3 4 5 7 8 Number of Nails per Nailing Edge Fig. 60. — Tests on nailed boxes for two dozen No. 3 cans; relation of number of nails to amount of rough handling required to cause loss of contents. It will be noted that boxes with 5 nails per nailing edge stood only a little over one-fifth as much as boxes with 7 nails per nailing edge. In boxes of the kind and size tested, 7 properly driven nails per nailing edge may be considered as good practice. The single piece end without cleats was shown in the 'com- pression and drop tests to be a poor form of construction. This conclusion is further substantiated by the drum tests. The resistance of white pine, red gum, and aspen boxes with 2 piece ends was increased 50 per cent, by the substituting of cleats (%" X IM'O for corrugated fasteners. Failure in the nucleated boxes was due to splitting of the ends, and did not occur at the joint. Similar tests on yellow pine boxes with and without cleats STRENGTH OF WOODEN PRODUCTS 106 showed an even greatej increase in resisting power in the cleated boxes. Several cases were observed where the nails in boxes for test were over-driven. In such cases the wood fibers were crushed and damaged and the board easily separated from the nail by pulling the head through the board or pulling the board endwise from the nail. Nails driven so that the heads are flush with the surface of the boards give the best results. In a number of boxes which were stored in a warm room before testing it was apparent that further drying had taken place, with resultant shrinkage. This shrinkage causes a side pull on the nails, which loosens them slightly. If the drying is carried far enough, splitting at the nails occurs. In either case the re- sisting power of the box is lowered. The storage of boxes in a warm room should evidently be avoided. It is also advisable to dry lumber for nailed boxes until it contains about 15 per cent, moisture, since this is the average condition that lumber would reach when stored in an unheated building or when in transit in closed cars. The following classification of box woods is based on the various box tests made by the Forest Service and on the tests to deter- mine the properties of woods, including strength, hardness, etc., and nail-holding ability. Classification of Box Woods Group 1. — Woods which are soft and from which nails are easily pulled. These woods require comparatively large nails. For boards }i inch thick 5d. nails spaced 2 inches apart are suitable. For boards % inch thick 7d. nails are needed spaced 2J^ inches apart. Alpine fir Mangolia Aspen Norway pine Balsam fir Noble fir Basswood Redwood Buckeye Spruce Butternut Sugar pine Cedar Western yellow pine Chestnut White fir Cottonwood White pine Cucumber Wiljow Cypress Yellow poplar Lodgepole pine Group 2. — Woods which are intermediate in softness. These are the 106 TIMBER harder coniferous woods, which are more subject to shakes and checks and to splitting in nailing or from rough usage than the woods in Groups 1 or 3. These woods are also more variable in strength and nail-holding ability. Ends made of these woods are preferably cleated. Size and spacing of nails are the same as in Group 1. Douglas fir North Carolina pine Hemlock Southern yellow pine Larch Group 3. — Woods which are comparatively hard and which are high in nail-holding power. These woods allow the use of smaller nails and thinner material than the woods in Groups 1 and 2. Box boards from woods in Group 3 may be He iiic^ or }4 inch thinner than those from woods in Groups 1 and 2. For boards Jf e inch thick (>f e inch less than Group 1) 4d. nails are satisfactory. For boards % inch thick (jg inch less than Group 1) 6d. nails are suitable. Ash Maple Beech Oak Birch Red gum Black gum Sycamore Elm Tupelo Hackberry Wirebound Boxes. — The tests on wirebound boxes, in which the binding wires are stapled to the sides, top, and bottom, showed that the numbfer of staples was an important factor in the resistance of the box. In boxes with comparatively few staples the resistance of the box was lowered by the veneer tearing out from the staples. Figure 51 shows the relation of the number of staples.in the boxes to the amount of rough han- dling required to break them. In Fig. 51 the average number of revolutions required to cause breakage and loss of contents with 24 staples per wire is taken as 100. The tearing apart of veneer and staples during the test was much less frequent in boxes with not less than 20 staples per wirie. The use of staples in securing ends to cleats proved unsatisfactory, unless the staples were driven at an angle to the gram; broad-headed nails gave more uniform results. The effect of storage conditions on boxes in which veneer was used was even more marked than on boxes made of lumber. Veneer absorbs moisture readily and dries out readily; and con- STRENGTH OF WOODEN PRODUCTS 107 sequently, boxes made of veneer, if exposed alternately to humid and dry conditions, will swell and shrink and tend to loosen the fastenings. The tests indicate that the drying of veneer for boxes to about 15 per cent, moisture, as in the case of box lumber, will give the best results. The drying of veneer to considerably below 15 per cent, is of little use as the material will soon reabsorb moisture under ordinary conditions. 4 8 12 10 20 24 Namber of Staples per Wire Fig. 51. — Tests of wire-bound boxes for two dozen No. 3 cans; relation of number of staples to amount of rough handling required to cause loss of contents. WOODEN VEHICLE PARTS The following laboratory tests^ were made to find the relative value of different woods for vehicle parts. The material for the tests was furnished in its finished form by manufacturers and the conditions of the test were made to conform as far as possible to the conditions that would occur in actual service. HicKOKY Buggy Spokes Tests were made on hickory buggy spokes to determine whether or not the system of grading was correct and to ascer- tain the relative strength and toughness of red and of white spokes. The material tested consisted of 500 1-inch hickory buggy spokes. These were graded at the factory by an experienced foreman, and each grade packed separately. The different 1 See Forest Service Circular 142, "Tests of Vehicle and Implement Woods," by H. B. Holroyd and H. S. Betts. 108 TIMBER grades and the number of spMkea in each, as graded at the factory in the order of their recognized commercial value, were as follows : Onde MumlMT of ipokea A-white 45 B-white 45 C-white 45 C-red 45 C-mixed 45 D-white 45 D-red 45 D-mbted 45 &white 45 E-red 46 CuUb 50 The method of testing spokes is shown in F^. 52. The Fio. 52. — Method of testing buggy gpokeB. spokes were compressed parallel to the grain and the force applied to the rim end of the spoke through the movable head of the testing machine. The spokes were cut to a length of 21 inches, the length used in the most common size of wheel. The regula- tion tenon was cut on the rim end, and this tenon was inserted in a hole in an iron block clamped to the movable head of the STRENGTH OF WOODEN PRODUCTS 109 testing machine. The heel of the spoke fitted into a second iron block resting on the platform of the machine. Vertically placed in the machine, the spoke was like a column with the rim and hub ends held in the same manner as in a wheel. The amount of bending or transverse deflection at the center was shown by a pointer attached to the spoke, and arranged to move over a hori- zontal graduated scale. The load at the first visible failure and the maximum load were noted, together with the corre- sponding deflections at the center; and in each case the test was continued until the spoke had reached a deflection of 2 inches at the center. All spokes were thus subjected to the same conditions. The factor representing the value of a spoke should include both strength and toughness. The greatest load held up by a spoke is a measure of its strength, and the amount of bending in a spoke when the first crack occurs is a measure of its toughness. The product of these two quantities gives a factor representing both strength and toughness. It is called the resilience factor. Table 15 gives the results of the tests arranged by grades. From this table it will be seen that the average weight and the average resilience factor were both considerably higher in the A-white spokes than in the other grades. A wide range between the maximum and minimum value for the resilience factor in any grade is noticeable, showing that the quality of the spokes varied in each grade. The C-red spokes have a higher resilience factor than either the C-mixed or C-white; D-red spokes have a higher resilience factor than the D-mixed or D-white; D-red ranks ahead of C-raixed and C-white; E-white has a slightly higher resilience factor than E-red. In investigating the relation between weight and resilience factor, only clear spokes were used. This was done in order to eliminate the influence of defects such as iron streaks, bird pecks, knots, cross grain, and wormholes; About 230 spokes were used. The weight and resilience factor of each of these spokes is plotted in Fig. 53. In this chart the weight of the spokes is shown on the horizontal scale, and the resilience factor on the vertical scale. The results of the tests, as plotted, are divided into three classes — red, white, and mixed color, distin- guished on the diagram by different marks. The average points through which the heavy lines are drawn were obtained by grouping points lying between certain limits of weight. Figure 110 TIMBER 53 shows that in the case of clear spokes the resilience factor in- creases directly with the weight in a fairly uniform manner re- gardless of color and that weight for weight the red and mixed spokes have as great a resilience factor as the white spokes — that is, the red spokes and the white spokes of equal weight are equal in mechanical value. Defects in spokes commonly include iron streaks, bird pecks, cross grain, knots, and wormholes. A spoke containing a 120 ^'V) 119 150 Weight in Grains when tested Fig. 63. — Spoke-test chart, showing relation between resilience factor and weight in clear spokes. wormhole is dangerous, as it is impossible to tell to what extent the spoke has been bored on the inside. Iron streaks are sup- posed to be caused by the infiltration of foreign coloring matter through bird pecks. Iron streaks and bird pecks, when they show only slightly, apparently do not affect the mechanical quaUties of a spoke. They are not generally found in the heaviest spokes, but among those of medium or light weight. Spokes failing from cross grain generally break into two pieces. Defects have greater weakening effect when near the center than when near the ends. The spoke tests definitely show three STRENGTH OF WOODEN PRODUCTS 111 Table 15. — Tests on Hickory Buggy Spokes (One-inch spoke; length 21 inches.) Grade Weight Maximum load Deflection at maxi- mum load Deflection at first failure Resilience^ factor (maxi- mum load multiplied by deflection at first fail- ure) A-white : Average . . . Maximum . Minimum. B-white : Average . . . Maximum . Minimum . C-white : Average . . . Maximum . Minimum. C-red : Average . . . Maximum . Minimum . C-mixed : Average . . . Maximum . Minimum . D-white : Average . . . Maximum . Minimum . D-red : Average . . . Maximum . Minimum . D-mixed : Average . . . Maximum . Minimum . E-white : Average . . . Maximum . Minimum . E-red : Average . . . Maximum . Minimum . Culls: Average . . . Maximum. Minimum. grams 177.5 190.3 165.5 164.5 182.5 146.0 150.5 182.0 119.3 157.2 173.3 144.4 155.5 186.0 132.0 144.2 176.6 118.2 148.6 174.7 131.1 145.2 166.2 112.8 147.8 174.9 124.7 146.1 180.2 106.5 156.8 191.4 116.5 lb. 3,899 5,005 2,750 3,332 4,780 1,615 2,873 4,220 1,720 3,080 4,525 1,835 3,102 4,095 2,110 2,815 3,835 2,025 3,235 4,950 2,010 3,171 4,250 2,065 2,985 4,180 1,400 3,009 4,500 2,050 2,738 4,025 1,776 in. 0.28 0.50 0.10 0.25 0.52 0.04 0.29 0.46 0.07 0.28 0.51 0.80 0.25 0.44 0.05 0.28 0.55 (a) 0.29 0.66 0.10 0.27 0.60 0.02 0.25 0.50 0.04 0.24 0.45 0.05 0.27 0.50 0.10 m. 1.22 1.75 0.85 1.31 2.00 0.72 1.22 1.75 0.75 1.36 2.00 0.08 1.27 2.00 0.75 1.13 1.75 0.65 1.25 2.00 0.40 1.24 1.90 0.70 1.13 2.00 0.75 1.08 1.85 0.50 1.18 2.00 0.33 in.-lb. 4,760 8,080 3,270 4,360 6,750 2,740 3,500 6,050 1,875 4,190 6,920 2,150 3,940 8,710 2,310 3,180 5,360 2,045 4,050 5,620 1,110 3,930 6,540 2,000 3,370 5,920 1,680 3,250 7,080 1,600 3,230 6,200 805 a Heading aot obtained* 112 TIMBER things: (1) That the system of grading buggy spokes did not correspond to their strength and toughness, (2) that the factor denoting the strength and toughness of clear spokes varies di- rectly with the weight, and (3) that red, white, or mixed spokes of equal weight have practically the same resilience factor. Oak and Hickory Buggy Shafts The object of the buggy shaft tests was to determine the rela- tive mechanical properties of hickory shafts graded as XX, which is a third grade, and shafts made of red oak, to show the possibilities of the latter in shaft construction. The shafts were 1% by 1% inches. The stock was secured in Mississippi, about 100 miles south of Memphis, Tenn. The material was kiln dried, steamed, and bent. Ninety-two shafts were tested — 46 XX hickory and 46 red oak. The conditions under which shafts are broken in actual service are so varied that no attempt was made to reproduce any one of them exactly. The rigging for testing the shafts was arranged to hold the butt end of the shaft so that the main part projected horizontally. A vertical force was then applied near the point, and the shaft bent upward. The amount of bending or deflec- tion near the point and the corresponding force required to pro- duce this deflection were noted at regular intervals. The tests were continued after maximum load until there was less than 20 pounds pull on the shaft, or until the shaft came in contact with the head of the testing machine. The weights of the two sets of shafts when dry were about the same; but the oak shafts, as they were tested, were slightly lighter than the hickory and contained 1.1 per cent, less moisture. The oak shafts closely approximated the hickory in strength values, but at the maximum load had 7J'^ per cent, less deflection. In only one quality was the oak decidedly inferior to the hickory — ^the ability to sustain a load after failure. Thirty of the 46 oak shafts were broken in two, and only 9 sustained more than 20 pounds load at the end 6f the tests; only 14 of the hickory shafts were broken in two, and 24, or more than half of them, sustained more than 20 pounds at the end of the test. A comparison of the maximum and minimum values given in Table 16 shows that the oak shafts were of much more uniform STRENGTH OF WOODEN PRODUCTS 113 quality than the hickory, in spite of the fact that many of the complete failures in the oak shafts were due to cross or spiral grained pieces that would be eliminated by careful inspection of market material. While these shaft tests are valuable as showing the poasibiUty of using red oak instead of XX hickory, they can not be taken as conclusive for a number of reasons. First, the tests were too Pio. 64. — Method of testing wagon ailes. few to give sufficiently definite results. Second, the oak shafts were not as carefully selected as commercial stock should be; straight-grained material would be to the advantage of oak in comparison with the lower grade of hickory. Third, the grading of the hickory down to the XX quality was based largely on the red color, which, as shown by the spoke tests, is no criterion of degree of strength; on a strength basis some of the red hickory shafts might have belonged in a higher grade. ill TIMBER 1 IS ■ s % 111 1 §f B° ■ 1 a 1 s-W ill jl 1 sis m 1 1 f 1 ll 5S .-:-"- .-:v 1 1 ^ ll ■2 si'^ *3^ 1 sf 5 ==* S:i ll < a 833 sis H If §55 S|s 1 22" '2* II ^ -=" "'•S 1 ■s 1 ifljifll 11 i i STRENGTH OF WOODEN PRODUCTS 115 Maple and Hickory Wagon Axles Tests were made to ascertain the relative strength of maple and hickory in the form of wagon axles, and to compare the effi- ciency of several styles of axle reinforcement. The material consisted of 48 rear axles of the common farm wagon design — 24 of hickory and 24 of maple. Three styles of construction were represented for each species — ^thimble skein, thimble skein trussed, and long-sleeve skein trussed. The axles selected were as nearly uniform in quality of wood as could be secured, and were representative of average seasoned stock. Figure 54 shows the method of testing. The axles, with hubs placed on each skein, were mounted on two I-beams, which rested upon the platform of a testing machine. Loads were applied by the testing machine at the two hounds by means of a straining beam attached to the movable head of the machine. Heavy car springs were placed between the I-beams and the platform of the testing machine, so as to make the load follow the axles after failure occurred, and reproduce' the continuous gravity action that would occur in a failure under service con- ditions. Rollers were used under all bearing plates in order to insure freedom in horizontal movement at the bearing points. The load was applied continuously until the maximum load was passed. Table 17.^-Strength of Maple and Hickory Axles Reduced TO Same Size Style of axle Maple Maximum load under test Maple in per cent, of hick- ory Maximum load (ad- justed to same sec- tion as hickory) Hickory llr^^^j" Maximum per cent. j ^ ory ^^^^^ *««* Hickory taricenas 100 per cent. Thimble skein : Average Maximum Minimum Thimble skein trussed : Average Maximum Minimum Long-sleeve ekein^russed: Average Maximum Minimum lb. lb. lb. 19,468 104 16,600 89 18,678 24,100 120 20,600 103 20,000 13,430 84 11,600 72 16.050 23,296 109 20,500 96 21,414 26,890 108 23,700 96 24,850 21,240 110 18,700 97 19,350 22,601 104 22,200 102 21,760 26,510 109 26,000 107 24,240 17,450 92 17,100 90 19,030 ICO 100 100 100 100 100 100 100 100 Tables 17 and 18 give the results of the tests. An adjusted set of results was calculated because the maple axles had a 116 TIMBER slightly larger cross section than the hickory. In the table the maximum load for the maple axles was reduced so as to give the load that would be supported by maple axles of the same size in cross section as the hickory axles. In all three sets the maximum load carried by the maple axles was slightly greater than that carried by the hickory axles. The adjusted maximum load carried by the maple axles, however, was less than that carried by the hickory axles in the case of the thimble skein and the thimble-skein trussed axles, and approximately the same in the case of the long-sleeve skein-trussed axles. It is noticeable that the strength values were more constant in the hickory than in the maple axles, which indicates a greater varia- tion in the maple stock. Table 18. — Per Cent, of Maximum Load Supported After Failure in Wagon Axle Tests Maple Style of axle. Hickory 1 ThiniHft ftVein 36 25 Thimble skein trussed 81 21 LonK-sleeve skein trussed 53 The amount of bending or deflection at maximum load was greater in the hickory axles than in the maple axles in all three sets, showing the greater toughness of hickory. The hickory axles were able to stand a greater shock than the maple axles. The load supported after failure at maximum Fig. 55. — Maple wagon axles after test; thimble skein. load was also much larger in the case of the hickory axles. When bending was continued beyond the maximum load, the maple axles had little strength left in them to support a load. The hickory axles, on the contrary, carried a large per cent, of their maximum load when subjected to the same conditions. STRENGTH OF WOODEN PRODUCTS 117 In the two sets of trussed axles the carrying capacity, ability to resist shock, and the load supported after failure at maximum load were all considerably greater than the same factors in the Fig. 66. — Hickory wagon axles after test; thimble skein. untrussed axles. In nearly every case the clamp and truss slipped while the axle was under test. In a number of axles received for test the manufacturers had Fig. 57. — Maple wagon axles after test; long-sleeved skein trussed. allowed the shoulder on the ends of the truss to project beyond the clamp. This allows the axle to bend considerably before the truss shoulder is pulled against the clamp and the truss Fig. 58. — Hickory wagon axles after test; long-sleeved skein trussed. brought into action.. Out of the 32 trussed axles, in only one instance did the truss rod break. The character of the fractures in the tested axles is shown in Figs. 55 to 58. These figures were made from photographs of 118 TIMBER individual axles taken after test. The maple untrussed axles, Fig. 55, generally failed near the center, showing a short frac- ture, while the failure in the hickory axles of the same design, Fig. 56, occurred near the skeins and showed a long, fibrous break. In the trussed axles. Figs. 57 and 58, the fractures were of the same general character, although less prominent. Maple is subject to a spiral grain difficult of detection, which sometimes causes sudden and complete failure. Oak, Southern Pine, and Douglas Fir Wagon Poles The object of the wagon-pole tests was to check the correctness of the grading of select and common oak poles, to ascertain the utility of the truss, and to determine the value of southern pine Fig. 69. — Method of testing wagon poles; trussed pole under test. and Douglas fir for pole manufacture, as compared with oak. The poles tested were of the common farm-wagon design and were representative of the respective grades. The following comprised the series of tests: 10 oak poles, select grade. 10 oak poles, common grade. 10 oak poles, common grade, trussed. 10 southern pine poles. 10 Douglas fir poles. All the poles were of the same dimensions. A device similar to the hounds on a wagon held the rear end of the pole rigid (see Fig. 59). The point of the pole was de- STRENGTH OF WOODEN PRODUCTS 119 fleeted by means of a tackle and suitable rigging, which trans- ferred the deflecting load to a platform scale where it was measured. Thus the poles were tested under a strain similar to that which occurs in service when the front wheels of a wagon are blocked and the team turns sidewise. The results of the tests are given in Table 19. The select poles were superior to the common poles in strength, toughness, ability to resist shock, and stiffness by from 23 to 42 per cent. The poles appear to have been graded upon a correct mechanical basis. The values for strength and stiffness were slightly higher in the case of the trussed poles. In toughness and shock-resisting ability, however, the reverse was the case. It is to be noted that more of the common untrussed poles than of the common trussed poles were cross-grained. The truss does not appear to be of any decided value from the standpoint of strength. In maximum load and stiffness the pine poles rank between the oak select and oak common poles. In toughness and ability to resist shock the values for the pine poles are less than for either set of oak poles. The fir poles were superior to the oak poles when not strained beyond the elastic limit. In strength and stiffness the fir ranked between the two grades of oak. The toughness and ability to resist shock was less in the fir poles than in the oak poles. The material in the fir poles was of a more uniform grade than in the oak or pine poles. Douglas Fir and Southern Pine Cultivator Poles Tests were made to determine the comparative value of Doug- las fir and southern yellow pine for use in cultivator pole manu- facture. The material consisted of 10 Douglas fir and 10 southern pine cultivator poles of the kind used in walking cultivators. The method of testing was similar to that used in testing the wagon poles (see Fig. 59). Table 20 gives the results of the tests. There was little dif-» ference between the pine and fir poles for most of the qualities measured, but the range was much greater in the pine poles than in the fir poles. This indicates less variation of stock in the fir poles. The load on the end of the fir poles at the elastic limit exceeded sgs ss:: S3S ssi ass g iil 5 Hi siS Sil 8ia gs§ 1 1 1 1 1 III III III III III i m IB ill III ill ■B.t; 1" IJ ill 11 III IP IB K ill 11 m §11 Bi i i 11 ■^ ^ m m K5 K! ■- 3S2 3S2 2S2 2!:2 Sg2 1 1 1 . s £ B^ lis HI TB m w ^ B% «!i gii ail §is . ' - SSS Hi : : : SgS SSS I ilJllllllWlllllll o o o (2 Q 8SS|5 gCJSS 8§SS2 scssa ii P :l ■ '.5l ill STRENGTH OF WOODEN PRODUCTS 121 that for the pine poles by 5 per cent, while the strength of the fir poles at maximum load was 5 per cent, less than that of the pine poles. The pine poles were inferior to the fir poles in stiff- ness, but had a greater ability to resist shock. In both sets of poles the majority of failures occurred near the point where the pole is attached to the framework of the cul- tivator. In the pine poles failure was complete in 7 out of 10, the poles breaking in two. In fir poles complete failure occurred in but 3 out of 10. Deduction from the Tests of Vehicle Parts The foregoing tests, while in some cases only suggestive, be- cause of the small number of samples tested, nevertheless show the value of laboratory tests as an aid in solving problems connected with the grading of vehicle wood stock, and the substi- tution of new species for old. The samples, representing dif- ferent grades, or classes, were selected by experts with a large experience in the vehicle industries, and were thoroughly representative. The spoke tests show an error of more than 50 per cent, in the grading system used, which was largely due to the tradi- tional prejudice and consequent discrimination against red hickory. No red spokes were allowed in the A and B grades, yet the tests show that a large proportion of the red spokes included in the lower grades should, because of their strength and toughness, have been included in the highest grades. The superiority of hickory in toughness and shock-resisting ability, as compared with maple, is brought out in the axle tests. It is probable that no native species combines such high values for strength, toughness, and other mechanical properties as the higher grades of hickory, which on this account are well fitted for such parts as are subjected to the greatest shock. The shaft tests indicate that red oak may be substituted for hickory of the lower grades in shaft manufacture. The difference in toughness between oak and such woods as southern pine and Douglas fir is shown in the results of the pole tests. Both of these latter species, however, when carefully selected, appear to be promising substitutes for second-grade oak in pole manufacture. The terms "second growth" and "forest growth'' are so loosely applied in the designation of grades that they are confusing ill TIMBER 5J |1 3 1 §11 III ii 1 m W 1 ! S s !i SI Si |i M sis iSS ^5 .-s.- «»■-- 1 1 1 ■^ SS2 SS2 s 8 ft ■i "5S "" t •3 1 3 ■ 1 a ISs 5Si P s ps III 1 i s SS2 S25 fill i! i i i STRENGTH OF WOODEN PRODUCTS 123 and might well be discontinued. These terms, as used by the trade, distinguish between good and poor wood and disregard the true meaning of the words. In order to use the terms in their correct sense, the particular species and conditions of growth would have to be known for each piece of material. Commer- cially this is impossible. In reality, a large per cent, of the stock which is classed as "second growth'' is "forest grown'' stock of good quality. As changes in the forest take place, as a result of lumbering and new growth, it may be asked at what point does the wood cease to be "forest grown" and become "second growth." The manufacturer can not definitely answer this question, and can not tell whether it may not be possible to secure both kinds of stock from the same tree. The term "black hickory "is also confusing when used to desig- nate a grade, because it is the accepted common name for certain species. There is much discrimination in the trade against defects such as knots and checks, but little is said about cross-grain. The tests have continually shown that in such material as spokes, axles, and poles, cross-grain is one of the most serious defects. Defects that will be removed in finishing should not be consid- ered defects by the inspector. Clauses in grading rules such as "Clear of any defects impairing the strength" are too indefinite. Weight is an excellent indication of the strength of dry hickory wood, although but little used in grading rules and specifications at present. The rate of growth that generally indicates heavy and strong material and the location of such material in the cross-section of the tree are shown in the following diagrams.^ •812000 a ftSOOO S 4000 «D •O a a ^ V • 5 30 \ /^ J k ^ I a, • Xi hJ 20 • a \^ i V \ I 10 J3 \ P 6 8 U 14 17 20 23 26 29 32 35 38 41 44 47 5 8 U 14 17 20 23 28 29 32 35 88 4144 47 Singi per Incb A*ngi per Incb DiAQBAM 1. ^ For a more detailed discussion of the strength of hickory see Forest Service, BuUetin 80, '* The Commercial Hickories," by A, T. Boisen and J. A. Newlin. 324 TIMBER The two diagrams show the variation in the strength and toughness of hickory for different rates of growth. The dia- grams indicate that hickory high in strength and toughness generally has from 5 to 20 rings per inch. Exceptions exist, however, in wood grown in dry situations in which the slow growing material may be strong and tough. 9 o a> A ■a A •4 *» 00 BO a •o a « 12000 V w "^ N "^ ^ 8000 •r 4000 2 1 C 8 10 luches from Oeuter of Tree u a M 0* b Oi • m Xi a M to p e H 40 -•s ^ 30 r > K A 2b — \ ■— ^ 10 b u u V o, CD r^ ^ ^ -V. .600 ^ .400 .200 2 4 G 8 10 Inches from Center of Tree Diagram 2. 2 4 6 8 10 rncbes from Center of Treo The three diagrams show the variation in the strength, tough- ness, and specific gravity (dry weight) of hickory at different distances from the center of the tree. In normal trees the strongest wood appears to be from 5 to 7 inches from the center and the toughest wood nearly at the center. Wood 3 to 7 inches from the center is generally high in mechanical properties. CHAPTER V THE SEASONING OF WOOD Importance of Proper Seasoning Methods — Fiber Satu- ration Point and Shrinkage — How Wood May Be Injured in Seasoning — Air Seasoning — Rules for Piling Lumber — Kiln Drying importance of proper seasoning methods Practically all wood before being put to use is either seasoned in the air or dried in a kiln. The main objects of seasoning are to increase the durability of the wood in service, to prevent it from shrinking and checking, to increase its strength and stiffness, to prevent it from staining, and to decrease its weight. The sooner wood is seasoned after being cut the less is the chance that it will be injured by the insects which attack unseasoned wood,^ or that it will decay before the time comes to use it. Wood that is to be treated with preservative needs in nearly all cases to be seasoned as much as wood that is to be used in the naturq^l state. Wood has a complicated structure, and the walls of its cells shrink and harden when moisture is removed from them, so that unless timber which is to be air-seasoned is piled in the right way , or conditions in the dry kiln are maintained in accordance with certain well-defined physical laws, the material is likely to warp or check, or in some way to be damaged seriously. Until recently proper methods of seasoning received comparatively little atten- tion from manufacturers; and large losses, especially among woods that are difficult to dry, were the rule. Sometimes as much as 20 to 25 per cent, of the seasoned lumber was rendered unfit for the use intended by defects which had their origin in the drying process. Since the quality of the finished product ^ The sapwood of seasoned hardwood is subject to attack and frequently to serious damage by powder-post insects. See Farmers' Bulletin 778, "Powder-Post Damage by Lyctus Beetles to Seasoned Hardwood," by A. D. Hopkins and T. E. Snyder, 1917. 125 126 TIMBER can be impaired seriously by wrong methods, the desirability of taking care to use right methods becomes apparent. FIBER SATURATION POINT AND SHRINKAGE Water exists in wood in two conditions:* (a) as free water con- tained in the cell cavities, and (6) as water absorbed in the cell ^ \;^ "•" ^ p^ [^ ■^c ^ ^^ ( ► .^ ^' .%^. ^ , "^ ^ ^ ( J>^ ^ <» >^ 5^ C ^ ( (J ^ ^ ^^ ^ --^ o ^ ^ ^ C^ ^ ^ o 2 2 4 6 8 10 12 14 16 18 20-22 24 26 28 80 82 34 86 88 40 42 44 Moisturo. in Percent of Dry Weiffhl: Fia. 60. — Effect of absorption of water on the volume of small, clear pieces of longleaf pine, red spruce, and chestnut. Each point is the average of from 5 to 11 specimens. The fiber-saturation point is at C The black dots are for specimens that were kiln dried and allowed to reabsorb moisture. walls. When wood contains just enough water to saturate the cell walls, it is said to be at the "fiber saturation point/' Any water in excess of this which the wood may contain is in the form of free water in the cell cavities. ^ The term "sap" sometimes is used wrongly to mean the moisture in wood, and at other times to mean the sapwood. Sap is formed, mainly in the early spring, in the leaves from water rising from the roots through the sapwood. In the leaves this water is converted into true sap, which contains sugar and soluble gums. The sap descends through the bark and feeds the tissues in process of formation between the bark and the sap- wood. The heartwood contains no sap. THE SEASONING OF WOOD 127 Removal of the free water has no apparent effect upon the properties of the wood except to reduce its weight, but as soon as any of the absorbed water is removed the wood begins to 113 112 111 no S 109 1 108 Q 107 106 4* 1 105 ^104 103 102 101 100 Fia. 61. — .— 113 4 4 A y /^ 112 111 guo 1? 109 / f D ryiui r Ci rve- V / / < / / Q 108 ( / o 107 M 4/U* / § lOo 3 «AP / 104 103 102 101 100 / r / /CJ Abe orpt ion Poin t } / / / 10 16 86 40 45 60 20 25 80 Moisture Percent Fig. 62. — Relation between the moisture content and the cross section of small, clear specimens of western larch. shrink. Since the free water is the first to be removed, shrinkage does not begin, as a general rule, until the fiber saturation point 128 TIMBER is reached. In the case of eucalypts and some of the oaks, however, shrinkage b^ins above this point. For most woods, the fiber saturation point corresponds to a moisture content of from 25 to 30 per cent, of the dry weight of the wood. If wood below the fiber saturation point is allowed to absorb moisture, it will swell. This swelling for most woods reaches its maximum at the fiber saturation point, and further absorption of moisture has no effect on the size. Figure 60 shows the increase in the volume of several different kinds of wood when allowed to absorb mobture after first Iwing thoroughly dried- Figures 61 and 62 show the relation between the area of the cross section and the moisture content for specimens of western hemlock and Pio. 63.— Shrinkage ai western larch, respectively, which were first dried out and then allowed to reabsorb moisture. Figures 60, 61, and 62 indicate that the rate of shrinkage from the fiber saturation point to moisture isquite uniform and likewise that the rate of swelling from moisture to the fiber saturation is quite uniform. From this it is evident that wood in an air dry condition {12 to 15 per cent, moisture) would have reached about one-half its possible shrink- Eige in drying from a fiber saturation point of 25 to 30 per cent. to per cent, moisture. Shrinkage is due to the contraction of the cell walls. Shrinkage of a piece of lumber in a direction tangential to the annual rings is about twice as great as in the radial direction. Lengthwise of the lumber it is very slight. F^ure 63 shows graphically the difference between tangential and radial shrinkage. Table 3, TUB SEASONING OF WOOD 129 Chapter II, gives the per cent, of shrinkage from a green to an oven-dry condition for the principal commercial species. HOW WOOD MAY BE INJURED IN SEASONING Checking. — Checking is caused by unequal shrinkage. If the outside of a piece of wood dries considerably faster than the inside, the surfEice in time will contract until it can no longer extend around the comparatively wet interior, and so will be torn apart in checks. Checks often are classified as end checks and face checks. End checking or splitting during seasoning causes nearly as much loss as face checking. Casehardening. — Casehardening or surface hardening occurs when the surface of wood becomes set in a partially dry condition while the interior is still wet. This condition results from too Pio. 64. — Sections cut from casehardened boards. rapid surface drying. If the interior of a casehardened piece of wood dries further, it tends to shrink, while the "set" condition of the surface tends to prevent it ftom doing so. As a result, stresses are set up in the piece. Figure 64 shows sections cut from casehardened boards, with a strip sawed from the center of each section. In A, the stresses cause the prongs to curve inward and bind on the saw. If the stresses are relieved by treat- ment with steam, as is sometimes done, and the board dried a second time, the resawed prongs, as shown in B, will curve outward, owing to a reversal of the stresses. This is termed "reverse casehardening,"' ' For further discusaion, see "Problems in Kiln-drying Lumber," by H. D. Tiemunn, Lumber World Review, September 25, 1915. 130 TIMBER Figure 65 shows the form taken by reaawed pieces of kiln- dry boards steamed for different lengths of time. In No. 1 the prongs curve inward, owing to casehardening. Nos. 2 and 3 also show a casehardened condition as indicated by the strips curving inward. In Nos. 4, 5, and 6 the casehardening has been eliminated by longer steaming and the resawed strips are straight. Pio. 65. — Resawed sections out from casehardened red gum boards steamed for different lengths of time after being kiln dried. (1), No final ateaming; (2) and (3), 18 minutea final steaming; (4), (6), and (6), 36 minutes final steam- ing; (7), 3 hours final ateaming. No. 7, which has been steamed still longer, shows a condition of "reverse casehardening," in which the resawed strips curve outward. Sections cut as shown in Figs. 64 and 65 may be used also to determine the distribution of moisture in lumber whether case- hardened or not. If not casehardened, such sections will curve THE SEASONING OF WOOD 131 inward as they dry if the lumber is wetter on the inside than on the surface, and outward if the reverse is the case. If the lumber ia uniformly dry, the prongs will remain practically straight. Honeycombing.— Honeycombing or internal checking occurs in casehardened pieces when the interior continues to dry and the surface remains fixed. In such cases splits appear in the interior. figure 66 shows examples of honeycombing in casehardened pieces. Warping. — Warping or twisting in lumber is due to unequal shrinkage. Some woods are much more subject to warping Fig. 86. — Honeycombed oak timbers, the result of casehardening. than others. The trouble can be prevented to some extent by careful piling, both during drying and afterward. Figure 67 shows badly warped pieces of lumber. Collapse. — In some woods, notably western red cedar and red- wood, when the very wet wood is dried at a high temperature, depressions appear on the surface of the boards, presumably due to the collapse of the plastic cell walls in certain places. If, however, these woods are heated above the boiling point while wet, the steam generated in the non-poroua cells causes the wood to bulge on the surface. Figure 68 shows collapse and bulging, or "explosion," as it is termed by the discoverer of the Brashness, — Wood subjected to high temperature treatments or very rapid drying may become brash or brittle and also dark- ened in color. Pieces of such wood will break suddenly when bent. Many complaints are heard of the overdryii^ of shingles which renders the wood brash and with "no life." AIR SEASONING Although the use of dry kilns is increasing steadily, most wood is still seasoned in the open air. If wood is kept in the air long enough, the moisture content finally comes into equi- librium with that of the surrounding atmosphere, and the wood is said to be air-dried. The rate of drying varies, of course, with time of year, species of wood, size and form of piece, and method of piling. Certain of these factors may be controlled or utilized in a way to hasten the drying process and lessen the likelihood of defects appearing in the material. THE SEASONING OF WOOD 134 TIMBER I 220 200 [ 1- Black Pine 3-Red Pine 6-Dousla8 Fii 180 \ \ 160 \ V \ \ 140 V \ il \ \ « \ 120 V O K ^ L 100 ^ ^ DC- > 200 180 3 160 I o H .. 140 « I 120 100 80 Ic -Black Pine 3c-Red Pine J 5c -Douglas Fur — 1 7c-White Fir| • s:^ *««^ 5c fc -o^ ^^ >J -^ 52= ^ 7c 2 4 6 8 Time Seasoning; -Months 2 4 6 8 Time Seasonint; -Months A B Fig. 69. — Southwestern ties. (A) Seasoning of ties at Pecos, N. Mez., cut in January and February. (B) Seasoning of ties at Pecos, N. Mex., cut in August, September, and October. (Black and red pine are local names for western yellow pine; black pine refers to young trees and red pine to mature trees.) 220 200 180 ^160 M H u 140 'gl20 100 80 60 lO-Lodgrepole Pine ll-Douslas Fir 12 » » Unpeeled 13 -Western Larch Peeled 14- •• »' Unpeeled IS-Doufflas Fir 16- »• »» :^ 5^ Sx N S^ s N ^ b^, N 1 N ^ H ^ 13 \ ^ L^ T H ^ ^, 11 ■< |n k ^*»i "^ ^ ^ k n^ n ^ y kJ r^ z: 16 ) p^ P P >— >15 -^ — o "liT ~^ 4 6 8 10 Time Seasoning: - Months 12 Fig. 70. — Northwestern ties. Seasoning of lodgepole-pine ties at Bozeman, Mont.; Douglas fir at Sandpoint, Idaho (curves 11 and 12); Pasco, Wash, (curve 15) ; and Tacoma, Wash, (curve 16) ; and western larch at Sandpoint, Idaho, cut in January and February; (the Tacoma ties cut in December and January) . THE SEASONING OF WOOD 135 Crossties, Poles, and Sawed Timbers. — The data in Pigs. 69 to 79, inclusive, collected by the Forest Service^ in various s aoo 17c '. - Hemlock-Unpeeled 180 1 18c- f» -Peeled 19c- M - „ 160 1\ 1 N \ ^ ^ ^^ .^ 140 N ^ r— 1 ^^ ^ Ui c ^^ Rw d r^ u N^ M ^*s t> 120 ^^ 19c k ^ o^ "^ >*-<: 1-50 100 80 _j _ 6 8 10 12 14 Time Seasoninsr - Months 16 18 Fig. 71. — Seasoning of hemlock ties at Escanaba, Mich., cut in August and September. 220 200 180 .160 t 120 E^ioo 80 60 23 -Loblolly Pine-Tex. 23 ' • > » ' > > 24*Shortleaf Pine „ 26-Iionffleaf Pine „ 26-Lioblolly Pine- Miss. \ ■» rv> \ ^ N\ \ \N ^ >« o^ 23- V yi N "^o^ ^ ? • ^ 26 •. 2 4 6 8 10 Time Seasoninsr - Months 12 Fig. 72.- -Seasoning of ties at Silsbee, Texas, and Ackerman, Miss.; cut in January and February. parts of the country show the rate at which crossties, poles, and sawed timbers of several species lose moisture when freely exposed * See "The Air Seasoning of Timber," by W. H. Kempfer, Forest Service, in Bulletin 161 of the American Railway Engineering Association. 136 TIMBER 6 8 10 12 14 Time Seaaonins - Montbii FiQ. 73. — Seasoning of hardwood ties in Southern States; cut in October, November, and December. 0? 3 O a M o 40 88 36 84 82 30 28 2C 24 I, N » ^ N K_ ^-^ A itao a Cut ^1 r Wl fSf^^T^^ fill 16 13 Fig. 2 4 G 8 10 12 14 Time Seasoning - Sfonths 74. — Seasoning of southern white cedar poles at Wilmington, N. C. 44 i 4C I 4* ,8 80 o a 32 I *» 28 •s ^4 L N s ^ — • ^ [ % V Y [ s \ \ ■-^. »» , s prii igC ut I Li^' ituu in G at I \ L ^ X V y \ V\ Intt r Ct \ V \n k. 1 V 1 ■V, ^N V Surau X 1 er { Jat H 2 4 6 8 10 12 14 16 Time Seasoainff - Months Fig. 75. — Seasoning of western red cedar poles at Wilmington, CiU. THE SEASONING OF WOOD 137 to the atmosphere. In some cases it was not possible to weigh the pieces for several days after they were cut. Freshly cut timber loses weight very rapidly in warm, dry weather. Ties 2 54 8 50 3 ^ ^42 k« y L 1 1 N "N^ n 1 rf^ k T^ ^ Ai tuan C it [ w ntei r^ t^ bk - — > >-^ b '■■■K j" i ^=M- -i . 6 16 15 20 8 10 12 14 Time Seasoning - Months Fig. 76. — ^Seasoning of chestnut poles at Thorndale, Pa. 22 ^4 2 4 6 8 10 12 14 16 Time Seasoning - Months Fig. 77. — Seasoning of northern white cedar poles at Escanaba, Mich, 38 9 30 34 •J 32 I •gso 28 DOUGLAS FIR i vV I ^ ^ *o. -o- ^^ -^i 8 X 1 6 ^ ^5; •'• • «« m . ■ . mm ..c ... *a. .^ ^ fi X i 1 Ji ly "v ^ ... •-- T I'q' Ma r " " "^ -CK W ^ ^ ~ ^ ^ r.-. -J". '^Z » w i "S« -•.1 * "^J ^ P 20 2 4 G 8 la 12 14 16 IS Time Seaaonins - Months Fig. 78. — Seasoning of Douglas-fir timbers at Eugene, Oreg. are in inches.) 22 24 26 23 (Dimensions given in some species lose 10 pounds in twenty-four hours. The rates of seasoning of the various species may be compared by the general trend of the curves. When the curves reach a horizontal 138 TIMBER position, the material may be said to be air dry, unless this happens at a time of year very unfavorable for seasoning. The ties were seasoned in piles of 50 each, and were exposed without cover. The ties on the top of each pile, however, were placed close together and served as a rough roof. The curves are plotted from the average weight of the ties. The weight per unit volume could not be used, as in many cases the volumes of the ties were not obtained. The poles were seasoned on skids in the open. The sawed timbers were seasoned in open piles under shelter. 46 fa 6 ^ I i 42 40 88 fT « » \ V LONGLEAFPINE \ k N>-N -o^ ...^ 6' k 1! "aD< iS'j 18' > m^ 1*1 4f> i« 15 s 5 i , ( J . I 1 1 2 1 4 16 18 20 . Tiaie SeMoninff Month FiQ. 79. — Seasoning of longleaf-pine timbers at Madison, Wis. Lumber. — Sawed lumber is generally dried by being piled in stacks with air spaces between the boards. In forming the stacks usually the boards are laid flat, with strips called stickers between courses or layers. A space also is left between each board in a layer and the adjacent board to provide for the cir- culation of air throughout the stack. Flat or horizontal piling may be of two kinds : (a) with the ends of the boards to Ward the alley — endwise piling, and (b) with the sides toward the alley — sidewise piling. Figures 80 and 81 illustrate the two methods. The stacks are arranged to slope from front to rear, and to lean forward so that water dripping from the top falls to the ground without trickUng down over the courses below. With either method of piling the stacks should be so located in the yard that the prevaiUng winds blow through them rather than against the sides of the stickers. Most lumber manufacturers and dealers use the endwise method of piling. A number, however, have adopted the side- wise method, which has certain advantages in the matter of air circulation. In endwise piling the stickers obstruct the pas- THE SEASONING OF WOOD ' 139 sage of air from back to front of a course, while in sTdewise piling the passages from front to rear are clear. Water which forces Fro. 80.— I,umber piled sidewiae on cement and metal foundations. its way into the pile is more effectively drained in sidewise pilii^, and the likelihood of sticker rot and discoloration due to the Fio. 81. — Lumber piled lengthwise on wooden foundation. accumulation of moisture, dust, and dirt against the stickers is lessened. The bottom boards in a stadc rest on skids, which in turn rest 140 TIMBER on foundations, preferably of stone, cement, or metal. Pieces containing rot should never be used for foundation timbers or skids, or allowed to remain in the pile. The vicinity of the pile should be kept clear of weeds. The use of concrete and metal foundations is especially feasible in retail lumber yards and in those maintained by wood-using factories. In retail yards, where economy in space often is the essential thing, the piles are high and a particular space usually is allotted to each class or species of lumber. In factory yards lumber often is held for a number of years before being used. In such cases the frequent renewal of wooden foundations under lumber piles entails considerable expenditure of time and money, to say nothing of the danger of infecting lumber by bringing it in contact with partly rotted foundation timbers. For these reasons foundations of a more permanent character are constantly THE SEASONING OF WOOD 141 growing in favor in retail and factory yards. .Figures 82 and 83 show foundations of this kind. Sawmill yards, on the other hand, often contain several million feet of material and cover several acres. Lumber cotoing from the saw is generally piled wherever most conven- )■ — Another type of permanent foundation. Steel raila are embedded in piers. The lumber ia fully 2}^ feet above the ground, insuring excellent ventilation. ient, provided it is placed at the distance from the mill required by insurance companies. Usually, economy in storage space is not essential, and piles of the same species and kind of lumber are likely to be found in a number of different sections of the yard. In addition, the stock is constantly being turned over, thus giving an opportunity to renew the foundation timbers at Fro. S4. — Method of providing drainage under lumber piles. comparatively small expense. A number of large lumber com- panies, however, have adopted concrete as a foundation material. Lumber-storage yards need to be reasonably well drained, or at least the contour of the ground should be such that water will not stand under the stacks after a storm. Otherwise, decay is 142 TIMBER apt to get a Btart and spread throughout the pile. Where the ground offers but poor natural drainage facilities, some artificial system of drainage is usually employed. Figure 84 shows the syBtem used in the yards of two large lumber companies in the southern hardwood region. This arrangement not only prevents the collection of rain water under the lumber pUes, but also gives the required slope to the stack, which on level ground has to be secured by building up the foundations. A top dressing of cin- ders has been found satisfactory in some storage yards. In- Tbe matter of providing good drainage in lumber yards and keeping them free from rotten pieces of lumber and tall grass and weeds is often neglected. Pieces of discarded lumber thrown aside on the ground, especially where weeds are prevalent and the ground is wet, readily develop decay-producing fungi' and serve as a source from which nearby stacks may become infected. ' See Chapter IV, Structural Timbera — CharacteriaticB Afiectin); Decay in Timber. THE SEASONING OF WOOD 143 It is not uacommon in yards to find partially rotted material piled against the lumber stacks (see Fig. 85) or to find fresh lumber stacked in direct contact with badly decayed foundation timbers. Under such conditions decay spreads rapidly to the sound lumber. Decaying timber which has been allowed to accumulate about the yards {see Fig. 86) should be collected and burned. This will not only arrest the spread of fungi but will also lessen the Fio. 86. — A highly insaoitary mill yard in South Carolina. Hundreds of thousands of feet of stored lumber have rotted in this yard as a result of these conditions. All this rotten debris should be removed and buroed. fire hazard. The piling of such material in one place is not suffi- cient; for the fungi will continue to thrive in it and to liberate Goimtless spores. These spores are blown about and find lodge- ment in stacks of sound lumber, where they develop and produce decay when the right conditions of temperature and moisture occur. Special attention should be paid to keeping the stickers free from infection. It is evident that the use of infected or 144 TIMBER partly decayed stickers in building up a stack of lumber is quite likely to cause decay in the lumber. When a stack is taken down, the stickers will be in much better condition for the next stack if piled on end in conical piles or stacked beneath the skids instead of being allowed to stay where they happen to fall (see Fig. 87) . In cases where lumber is stacked for a comparatively short time under conditions where it is exposed to infection, no marked deterioration may be evident. Decay may, however, be present Fio. 87. — Piling sticks lying on the ground at a mill in South Carolioa^ showing the insanitary method of handling them. Such sticks lying for only B week or two in contact with fungUB-infect«d ground may themselves beoome seriouBly in/ected, and may in turn pass the decay on to the lumber stacks. in incipient stages ready to progress further should the liunber be placed under moist conditions. It is highly probable that many of the failures in timbers in important structures in recent yeEirs have been due to the use of timbers that were infected before placement in the structures. Timbers not infected are, of course, much more able to resist decay. The railways and tramways common in lumber yards generally contain more or less rotted timber, and may become a dangerous source of infection. Little attention is paid to preservative THE SEASONING OF WOOD 145 treatment, as timber for renewals is naturally plentiful. It is well worth consideration, however, as a means of lessening the danger of infecting lumber piled for storage, as well as of reducing the frequency of renewals and the usual attendant interruptions to normal operation.^ Rules for Piling Lumber The following set of rules for piling lumber covers the more important points to be observed in the construction of founda- tions, shape of stack, arrangement of stickers, etc. : Foundations {Endwise or Sidewise Piling), (a) The foundations should be strong, solid, and durable. (b) The top of each foundation should be level, and from front to back the top surface of the parallel skids should be in align- ment, so that the lumber to be piled will bear equally upon each one. (c) The front foundation should be raised above the second, and the second above the third, etc., to allow a slant in the stack of 1 inch to every foot. (d) The foundations should be spaced not over 4 feet apart, except for heavy planks and timbers. (e) The front foundation should be of sufficient height to provide space for free circulation of air under all parts of the pile. Lumber {Endwise Filing), (a) Skids, preferably 2 by 4 inches, should be laid on top of the foundations. (6) Boards of equal length should be piled together. (c) The ends of the boards should rest upon the front and rear skids. • {d) A space of approximately three-fourths of an inch should be left between boards in the same layer. (e) Lumber piled in the open should have the front ends of boards in each layer slightly protruding beyond the end of the layer beneath, to give a forward pitch to the stack. Lumber (Sidewise Piling). (a) Skids, preferably 4 by 6 inches, should be placed across the foundations at about 4-foot intervals. The number of skids depends upon the thickness of the lumber. ^ For a farther discussion of timber storage with reference to decay, see U. S. Department of Agriculture Bulletin 510. "Timber Storage Conditions in the Eastern and Southern States with Reference to Decay Problems," by C. J. Humphrey. ♦ 146 TIMBER (6) Boards of equal length should be piled together. (c) The boards should be placed on the skids, with about three-fourths of an inch between boards in the same layer. (d) Lumber piled in the open should have the front board in each layer project slightly beyond the board in the layer beneath, to provide a forward pitch to the stack. Stickers {Endwise or Sidemse Piling), (a) Stickers should be of uniform thickness, preferably seven- eighths of an inch for 1-inch lumber and l}^i inches for 2-inch lumber. Their length should be a few inches in excess of the width of the pile. (6) Stickers should be placed upon the layer of boards im- mediately over the skids and kept in alignment parallel to the front of the piles. (c) The front and rear stickers should be flush with^ or pro- trude beyond, the ends of the boards. Roof Protection {Endwise or Sidewise Piling). Cover boards, as a roof protection, should be laid on the top of the pile, extending a few inches beyond the front and rear ends of the stack. Spacing Stacks {Endwise or Sidewise Piling), Space between the piles should not be less than 2 feet; 4 or 5 feet is better if yardage conditions permit. Dimension of Stack {Endwise or Sidemse Piling). The customary width of stacks is from 8 to 16 feet. The height is governed by the size and character of the lumber and by the methods of moving it. Treated Ends {Endwise or Sidewise Piling). The ends of lumber 2},i inches thick or over, unless of the lower grades, should receive a brush treatment of paint or some Uquid filler. The rules just given are based on information obtained through field investigations and from lumber manufacturers and whole- sale and retail dealers, and accord with the best lumber-piling practice in general commercial use. Certain species of wood, however, require particular care in air drying, and in this case slight variations from the rules are necessary in order to secure the best results. Some lumbermen in the South, for example, find that thick red oak checks badly on the ends, and in air« THE SEASONING OF WOOD Piu. S8, — Sun shields used to reduce nheching in thick red oak timber. Vm. 89.— Lumber piled s 148 TIMBER drying such stock have adopted the scheme of protecting it with Bun shields, as shown in Fig. 88, which they claim reducea end checking to a minimum. Mills cutting red gum formerly experienced difficulty in drying the lumber, on account of its tendency to warp. This, however, has been largely overcome by the exercise of care in seasoning. In erecting a pile of gum lumber, stickers are placed every 2 feet apart, some lumbermen claiming that 18 inches is none too close to obtain the best results. Another scheme in more or le88 general use among gum-lumber manufacturers is to construct the pile so as to have a flue or "chimney " in its center, thus pro- FiO, 90. — Pole drying yellow poplar lumber. viding ample air circulation vertically through the stack, as shown in Fig. 89. Green cottonwood, basswood, and yellow poplar lumber are likely to stain badly when piled. Accordingly, a number of lumbermen either end-dry the material or pole-dry it for a week or two and then place it in a "stuck" pile. In end drying, the boards are stood up on end, edge to edge, under a specially built shed, with stickers arrangi'd horizontally one above the other at specified distances. Such a pile presents exactly the appearance of a regular lengthwise pile of lumber set up on end. THE SEASONING OF WOOD Fia. 92. — Lumber yard of a sawmill ia the Lake Staws. Not« fine ap- pearance of lumber piles. The discarded material in the foreground is, however, a dangerous source of infection and should be burned. 150 TIMBER Figure 90 shows a quantity of yellow poplar lumber being pole dried; and Fig. 91 shows the frame used tor the purpose. Hickory and ash lumber frequently check badly when air dried. Lumbermen in the southern hardwood region have found that the checks will close up entirely if the lumber is first stuck piled for six to eight months and then bulk piled and protected by good covering, preferably shed. The mechanical weakening effect of such checks, however, still remains. Fia. 93. — A well-kept lumber yard. Figures 92 and 93 show lumber piles in yards where careful attention has been given to piling and yard arrangement. KILN DRYIHG Lumber is kiln dried when there is need for seasoning it quickly, or when the manufacturer does not wish to carry large stocks in his yard. A kiln is used also when partially air-seasoned or even fully air-seasoned material is to be dried further for spe- cial uses. The main problem in kiln-drying lumber is to prevent the moisture from evaporating from the surface of the pieces faster than it is brought to the surface from the interior. When this THE SEASONING OF WOOD 151 is not prevented, the surface becomes considerably drier than the interior and begins to shrink. If the difference in moisture content is sufficient, the surface portion opens up in checks. The evaporation from the surface of wood in a kiln can be controlled to a large degree by regulating the humidity, tem- perature, and amount of air passing over the wood. A correctly designed kiln, especially one for drying the more difficult woods, should be constructed and equipped in a way to insure this regulation. A dry kiln may consist simply of a box in which lumber can be heated, or of a good-sized btdlding or group of buildings (battery) containing steam pipes, condensers, sprays, and various air passages capable of adjustment to regulate the amount of ven- tilation. The elaborateness of the kiln depends, of course, mainly upon the value of the lumber that is to be dried. For lumber worth $100 per 1,000 board feet, it will pay to use more careful drying methods than for material valued at $20 or $25 per 1,000 board feet. Types of Kilns. — Kilns for drying lumber may be divided into two general classes: (a) compartment kilns, and (6) progressive kilns. In compartment kilns the conditions are changed during the drying process, iand all lumber in the kiln is dried at one time. The conditions at any time during drying are uniform throughout the whole kiln. In a progressive kiln conditions at one end differ from those at the other, and the lumber is dried progressively by being passed through the kiln. Compartment kilns are used when it is desired to dry lumber of various sizes and species; progressive kilns are generally used wKere uniform stock is handled. The methods of operation generally used in lumber kilns are: (a) natural ventilation (see Fig. 94), (b) condensing (see Figs. 95 and 96), and (c) superheated steam (see Fig. 97). In kilns operating by natural ventilation, the hmnidity or dampness is controlled by the use of escaping steam and evapo- rated moisture. Circulation in progressive kilns is largely longi- tudinal and in compartment kilns transverse. Moist air is allowed to escape from the kiln. In condensing kilns the hmnidity is controlled by recirculating the air, which has taken up water from the lumber, across water pipes or through water sprays. The temperature of the pipes or sprays governs the amount of water that condenses from the 152 TIMBER air, and oonsequently regulates the humidity of the air when re- heated before being passed over the lumber again. The circula- tion of air may be either natural or forced. Condensing kilns lire generally of the compartment type. Flu. 94. — Scheme of s progressive kiln operitt«d by natural veotilstioii. The entering air passes through the heating coiLs beneath the lumber piles then up Uirough tha lumber and out by way of the chimney. Steam may be ' admitted to raise the humidity. Fio. 96. — Scheme of a progreseive blower kiln with a condenser for resulating the humidity. Air more or I^ss saturated with moisture taken up in paasiiiit over tbe lumber is drawn from the green end of the kiln through cold-water coils, where it is cooled and part of the moisture it coDt«ina is deposited. After passing through the fan, the air is heated in the steam cuila and made relativ^y drier. At the dry end of the kiln this heated air passes over lumber already partially dry and gradually removes moisture until the proper degree of dryness is reached. When this occurs the lumber truck at the dry end is removed and a truck with green lumber run in at the green end By varyini; the temperatures in the cool- ing and In the heating coils the conditions in the kiln may be regulated. Kilns operating with superheated steam are used only where tbe species to be dried are not injured by high temperatures, and wbere fast drying is advantageous. THE SEASONING OF WOOD 153 Ljimber may be piled on the trucks which carry it into the kiln in any one of three ways (F^. 98) : (a) flat or horizontal, (6) edge or vertical, and (c) inehned. Flat piling is best for longitudinal circulation. It is not so well adapted for transverse circulation, and is not economical for downward circulation. Vertical piling increases the truck capacity, as there are no Pio. 96. — Cioss sectioD of compartmeat spray kiln developed by U. S. Forest Service. The air is heated by tlie coils (H), riseH between the piles, and passes through them, taking up moisture /rom the wood. The cooled and heavier sir then flows downward through the spray {F) and the flue (B) and then through the baSle plates (i>) to tbe heating coils again. The condenser ((7) is available if necessary. The temperature and velocity of the spray, the temperature of the heating coils and condensers, and the method of piling the lumber can ba regulated to obtain the proper conditions for drying. It is frequently desirable to leave a space between boards in the same layer instead of placing them dose together as shown. vertical spaces between the boards. Probably it is the best method for downward or any fast circulation. Provision has to be made, however, for keeping the boards in place in the stack. Inclined piling allows, for a definite movement of air either 154 TIMBER downward or upward (forced draft) and is In many cases an improveroent, as regards circulation, over horizontal or flat piling. Some kiln operators using the flat or horizontal method of piling report excellent results from the construction of a V- ahaped opening in the center of the truck pile. Such openings are from 2}4 to 3 feet wide at their base, and from 3J^^ to 4 feet h^h. Where this practice is followed it is customary Fto. 97. — Cross section of a. compartment kiln operatiiiK with supertieat«d steam. Edge stacking with a device for taking up ahnnkage la shown. Heating coils are located on each side of the kilo. Steam is admitted between the pile and the coils. The circulation is down through the pile and up on each side. The temperature and quality of steam and the temperature of the heating coUs can be regulated to obtain the proper conditions for drying. also to place the boards in the layers closer together as the top of the stack is reached, to force greater lateral circulation. In loading lumber on kiln trucks by any one of the three methods mentioned, the stickers should be of a uniform thickness and arranged in the piles in alignment. It is advisable not to attempt to dry various thicknesses of THE SEASONING OF WOOD 155 lumber together. Thick lumber takes longer to dry than thin lumber; and when different thicknesses are mixed the operation INCLINED PILES FLAT OH H0R120NT^L PILES has to be governed by the thick stock, to the possible detriment, or at least the unnecessarily long drying, of the thin stock. 156 TIMBER Preliminary Treatments. — ^Lumber to be kiln dried is sometimes steamed in a separate compartment before being placed in the kiln proper; especially where the kiln is not designed for moist- air treatment. The object of the steaming is to heat the lumber and thus make easier the transmission of moisture from the interior to the surface, and also to moisten the surface in case it has become casehardened or "set" during partial air drying. Other effects, also, are produced, which to a greater or less extent change the properties of the wood. Changes of a chemical nature apparently take place; for example, "sap'* is changed by "cooking," as indicated by a darkening of the wood, the degree of coloring depending upon the temperature and duration of the process. The pressure and duration of steaming desirable in kiln drying have not yet been thoroughly worked out. Durations of from five minutes to twenty-four hours or longer and pressures ranging from atmospheric to 50 pounds gauge have been used in practice. The higher the pressure the greater is the effect pro- duced, and the longer the time the more thoroughly the treatment penetrates the wood. Experiments have shown that a pressure slightly above atmospheric for twenty-four hours will slightly darken 2-inch maple cleisir through, and a pressure of 40 pounds will turn oak and probably other hardwoods almost black. Even where the strength of the wood is not the primary consideration, it probably is not safe to exceed 15 pounds gauge pressure (250° F.), except for special purposes. In transferring lumber from a compartment for preliminary treatment to the kiln proper, every care must be used to avoid a sudden change in humidity. The Process of Drying. — After the wood has been heated thoroughly in a hmnid atmosphere, either in the kiln proper or in a separate compartment, it is ready to have the moisture removed by evaporation from the surface. In kiln drying, uniform circulation apparently is the most important thing to be secured. The fact that air when it enters the drying chamber will be cooled, and therefore will tend to fall, should govern the method, of piling and the directions of circulation.^ This means that the air should be allowed and as- sisted to pass downward through the pile, either by entering at the 1 See "The Circulation in Dry Kilns," by H. D. Tiemann, U. S. Forest Service, Lumber World Review, May 10 and June 10, 1916. THE SEASONING OF WOOD 157 top of the pile or by an adaptation of this principle to other methods of piling. The rate of evaporation may be controlled best by regulating the amount of moisture in the air (relative humidity) circulating about the lumber in the kiln; it should not be controlled by reducing the air circulation, since a large circulation is needed at all times to supply the necessary heat. Air at 100 per cent, relative humidity contains all the water it can carry and has no effect in drying wood. If, however, the humidity is reduced to 80 per cent, and the air then passed through a pile of wet lumber, the air can take up a certain amount of moisture. If drying does not progress rapidly enough with the circulating air at 80 per cent, humidity, it may be reduced still further. This may be accompUshed by ventilation, by condensers, by water or steam sprays, or in a number of other ways. If checking begins during the drying process, the humidity should be in- creased until it stops. Steam jets in a kiln are often Useful for this purpose. In changing the humidity, the circulation should not be reduced. A large body of moving air is necessary in order to keep a uniform temperature clear through to the center of each piece of wood in the pile and at the same time supply the heat required for evaporation. If sufficient circulation is not se- cured, the supply of heat for both purposes will be lacking and the material will not dry uniformly. The conditions suitable for drying lumber of a certain kind are dependent on the use to which the wood is to be put. For some purposes a decrease in strength due to rapid drying is allowable so long as the appearance of the. wood is not harmed and it stays in place and does not check. Inside finish, siding, and certain kinds of furniture are examples. For other purposes, such as airplane, vehicle, and handle stock, the full strength of the wood must be preserved, and the drying slowed down until there is no injury to the mechanical properties of the wood, even though the appearance may be entirely satisfactory. The conditions that will generally give satisfactory drying and preserve the strength of the wood are a temperature of from 110 to 140° F. or higher at the start, depending on the kind of wood and the thickness of the pieces, and a humidity of from 80 to 85. The temperature is gradually raised as drying proceeds to a final temperature of 135 to 160° F. or higher while the hu- midity is gradually lowered to around 30, depending on the thick- 168 TIMBER nesB of the lumbier and the degree of drynesB required. The time required for drying depends on the thicknees of the stock and the amount of moisture it contains. Some of the softer woods in the form of 1-inch boards may be dried in a few days to 10 per cent, moisture, while thick (3-inch) oak stock may require three months or more. The lumber should be inspected at frequent intervals during the run. If small checks appear, the humidity should be raised and probably the temperature lowered. A sample about 2 feet long may be cut from a typical piece in the stack to be dried before the run starts and its moisture and weight determined. This sample should then be replaced in the stack. ■ By removing and weighing the sample during the run the rate at which drying is proceeding throughout the pile can be closely estimated. Sections cut from pieces in the stack at the comple- tion of the run and resawed as in Figs. 64 and 65 may be used IE I.. Fia. 99. — Typical oonditiona in a kiln during a run, to show whether the lumber is casehardened or not, and also to show if the moisture is evenly distributed. Sections may also be cut into pieces and the moisture determined in the interior and surface portions to show the moisture distribution (see "Method of Determining Moisture in Wood" in Chapter III). Figure 99 shows the conditions in a kiln during a run, with ref- erence to temperature, humidity, and moisture in the wood. It will be noted that the humidity is kept high at first and lowered gradually. The temperature is held at a certain level for some time and then raised. The moisture is lowered gradually to a final condition of less than 10 per cent. The maximum rate of drying at a given temperature is reached when moisture is evaporated from the surface of the wood just as fast as it is transmitted from the interior. This rate is fixed THE SEASONING OF WOOD 159 by the rate of transmission of moisture within the wood, and varies with different woods. . The temperature of drying apparently influences the rate of transmission of moisture within the wood. The higher the tem- perature of the wood the more rapid is the rate of transmission of the moisture, and hence the rate at which the moisture may be evaporated safely. This, of course, applies only to temperatures below those which might result in injury to the wood. Figure 100 shows theoretical conditions in a kiln where both preliminary and final steaming are used. Casehardening that 170 160 ^160 2 ol40 Sl80 s |l20 ^110 d *100 t s a a /y L i 1 — ^ [^ p^ A ^ i V^ V ^ / ^^ •d 1 / V u y^ PI oal 3tea mln \l — ( J\ v i lo ^ r- ^pj «ltll lina tB «am Ing "■" ^ k ^^ ^ ^ »<»J/cj /** i ■^ \ <5 ^ i" N \ "X ^ -Af« » ^ H^-e V— -■«io Stug 9/0 H^o, id "^ — A t 90 80 70 CO 60 40 80 20 10 \ 2 3 4 5 6 7 8 9 10 11 12 13 U 15 16 17 18 19 20 21 Time in. Kiln in Days Fia. 100. — Theoretical conditions in kiln while dicing lumber 2 inches thick of the lighter pines, spruces, etc. occurs during the drying is removed by a few hours steaming at the end of the run. The oaks, hickories, and other heavier hard- woods require a longer period of drying to avoid checking and excessive casehardening. Lumber 1 inch thick can be dried in one-half the time given or less. Drying tends to render wood more or less brittle. Although the strength of wood increases with its degree of dryness, yet wood which has been dried and resoaked is less resiUent than when 160 TIMBER green. Therefore, where strength is the prime consideration, it is preferable not to dry the wood considerably beyond the degree at which it is to be used. The final stage of kiln drying is generally conducted at a humidity somewhat below the actual humidity that on long exposure would produce the same average moisture condition. This is done in order to hasten the drying and to make it uniform throughout each piece. Storage of Dried Lumber. — Since wood is a very hygroscopic substance, lumber stored under certain conditions will tend to come to a moisture content corresponding to the temperature 85 80 26 |20 I r £io COMPOSITE CURVE SHOWING THE MOISTURE CONTENT OF FIVE WOODS AT DIFFERENT HUMIDITIES AND ORDINARY ROOM TEMPERATURES • White Oak o Sitka Spruce 9 Black Walnut • Yellow Birch • Aah %] r > )30 • •J^ ^30 OK •i 6 25 Ml - y r 15 10 5 ^t>8 y"^^ > ^^ ■r^ *-' .--^' 1^^^ IJ 23 70 80 90 ICO 30 40 50 00 Per Cent Relative Humidity Fig. 101. — Composite curve of moisture content of five woods at different humidities and ordinary room temperature. and humidity under which it is stored. Lumber kiln dried to a moisture content of 6 or 8 per cent, and then stored under an open shed will reabsorb moisture up to about 15 per cent., while lumber dried to 15 or 20 per cent, moisture and then stored in a wood-working shop will tend to dry out to about 6 per cent. The time required for lumber to reach a condition of moisture cor- responding to the conditions of storage depends largely on the thickness of the material. The humidity of the storage condi- tions largely determines the final moisture. The moisture con- tent reached by lumber stored under ordinary room tempera- tures for different degrees of humidity is shown in Fig. 101. THE SEASONING OF WOOD 161 The data were obtained by storing samples of five different woods under different humidities until their weight was constant. There was no practical difference in the moisture content reached by the different woods at the same humidities. The proper humidi- ties for storing lumber which it is desired to hold at a certain moisture content are shown by the curve. At higher tempora- ■ tures the moisture content reached by the wood for any certain humidity would be less. For temperatures around 200** F. a humidity of about 80 would Ke required to hold wood at a mois- ture content of 10 per cent., while at room temperature -^ about 70° F.) a humidity of about 55 corresponds to 10 per cent, moisture. CHAPTER VI THE GRADING OF LUMBER BY MANTTFACTDRERS' ASSOCIATIONS' Principles op Lumber Grading — Manufacture and Dis- tribution OP Graded Lubcber — Hardwood Lumber Grading — Hardwood Associations — Comparison op Rules — Softwood Lumber Grading — General Char- acter OF the Rules for Softwoods — ^Description of Typical Rules PRINCIPLES OF LUMBER GRADING The grade of a piece of lumber is at present determined by the nmnber, size, and location of the visible defects it contains. Clear pieces are placed in the highest grade, pieces with a few defects in the next grade, and so on down to the lowest grades or culls. Defects include knots, stained sap, shake, wane, rot, pitch pockets, splits, and seasoning checks. In lumber for some pur- poses the presence of certain defects is allowable; for other uses only clear material is suitable. Where only clear pieces are suitable the value of the raw material depends upon the number of such pieces of a certain size that can be obtained from it. In the case of sheathing for a house, over which the siding is nailed, knots, stained sap, and seasoning checks in reasonable quantity are allowed because they do not injure the lumber for that pur- pose. On the other hand, material for certain classes of furniture, table tops for example, must be clear and hot less than a minimum width and length, so that the suitability of lumber for such use is entirely a matter of the clear cuttings that it will yield. Dif- ferent uses call for cuttings of different kinds. Some products, such as flooring, require long, narrow cuttings for their manufac- ture; others, such as furniture stock, require short, wide cuttings. In some uses (highest grade flooring) one side only need be clear ^ See paper by H. S. Betts and J. C. Nellis, Forest Service, Department of Agriculture. 162 THE GRADING OF LUMBER 164 TIMBER because the other does not show, while in other uses (best grade door stock) both sides of the cuttings are exposed to view, and should be clear. In certain uses, such as siding, one edge is covered when it is finally in place, so that some defects in the covered edge are allowable and the raw material is selected with this in mind. Grading rules for lumber are generally prepared by associations of lumber manufacturers whose members cut certain species which grow in the same region. Figure 102 shows the names and headquarters of the principal lumber manufacturing associations and the woods covered by their grading rules. MANUFACTURE AKD DISTRIBUTION OF GRADED LUMBER In the manufacture of graded material the trees are felled and the logs cut into standard lengths to a top diameter in the tree varying from 12 inches to 4 inches, depending on the species and on the condition of the market. When there is a large demand for low-grade material, as in prosperous times, it is possible to carry the utilization of the tree a good deal further than when the demand for low grades is very slack. This applies both to the smallness of top logs which can be used at a profit and to more or less defective logs which will not yield high-grade material. In some parts of the country logs are divided into two or three grades, depending on their size and the defects they contain. Log grading is generally based on the proportion of the higher grades of lumber that can be obtained from them. The proportion of the different grades that are obtained from a log depends to a considerable extent upon the judgment and skill of the sawyer. This is probably true to a greater extent in hardwoods than in softwoods. There is more opportunity for the exercise of judgment in sawing the more valuable hardwoods than in sawing the conifers because in operations in conifers the logs are more regular and the methods more standardized. In some parts of the country, especially New England, it is cus- tomary to manufacture what is known as "round edge*' lumber. That is, the logs are simply sawed into flitches at a single setting, no attempt being made to trim the edges of the material. About 10 per cent, more lumber, board measure, is obtained by this method than by sawing all boards with parallel edges. Such lumber is usually loosely graded by local unwritten rules. THE GRADING OF LUMBER 165 The distribution of lumber from the mills where it is manu- factured is influenced largely by the grade of the material and its corresponding price. High-grade lumber can be shipped comparatively long distances and still yield a profit to the manu- facturer in spite of a high freight charge. Low-grade material, however, of comparatively little value can stand only a short haul. On this account, it is generally only the higher and medium grades of species growing in different regions that come into competition. Woods put to special uses and structural timbers cut only in certain regions do not follow the general rule. The distribution of grades is also affected by the pros- perity of the country. In good times the demand for tlie lower grades greatly increased, as a result of increased building and construction of all kinds; prices rise, and it is possible to ship low-grade material further and still make a profit on it. High- grade stock is much less influenced in both distribution and price by changes in business conditions. HARDWOOD LUMBER GRADING Hardwood Associations. — Nearly all hardwood lumber pro- duced in North America is graded according to the rules of two lumber associations, the National Hardwood Lumber Association and the Hardwood Manufacturers' Association of the United States. Fifty years ago practically no hardwood lumber was graded. There was only a very limited demand for it in the wood-using industries; the chief problem of manufacturers was finding a market, and they sold their output "mill run" to jobbers, wholesalers, and other buyers. The first attempt to grade hardwood lumber on the market was made by an association of wholesale dealers in New York. The New York Lumber Association formulated rules for use in trading on the New York market and for export lumber. These rules, naturally, were extremely favorable to the jobber and wholesaler and admitted onl}' entirely clear stock in the upper grades. Outside of New York there were no rules in force, until in 1894 the National Wholesale Lumber Association was or- ganized to establish uniform grading rules for hardwoods. This association, by judicious revision of the old New York rules, succeeded in obtaining members representing both wholesalers 166 TIMBER and manufacturers. In 1900 the association changed its name to the National Hardwood Lumber Association. In the mean- time the manufacturers of hardwood lumber in the Middle States had formed an organization of their own and adopted indepen- dent rules. This association was not successful and was finally- merged with the National Harwood Lumber Association about 1900. Many of the manufacturers of the Middle States and especially in the South withdrew when the merger took place and organized the present Hardwood Manufacturers' Association of the United States. There are other hardwood associations in existence at the present time, but they use the rules of one or the other above associations, having no separate rules of their own. The members of the Hardwood Manufacturers' Association are manufacturers. They operate largely in the central and southern hardwood region. The National Hardwood Lumber Association is the larger association, and is comix)sed of manufacturers in the northern, central, and southern regions and wholesalers in all the principal distributing points. The grades adopted by these two associations for the various kinds of hardwood lumber are shown in Table 21. Table 21. — Grades Adopted for Hardwood Lumber Products national hardwood lumber association August, 1917, Rules Kinds of Woods Graded Ash Butternut Hickory Poplar Basswood Cherry Locust Red gum Beech Chestnut Magnolia .Sycamore Birch Cottonwood Mahogany Tupelo Black gum Cypress Maple Walnut Buckeye Elm Oak Willow Hackberry Pecan Oak, Plaiiv-sawed, Red and White Product Grades Lumber. Firsts & Seconds Selects No. 1, 2, 3 Common Sound Wormy THE GRADING OF LUMBER 167 Table 21. — Grades Adopted for Hardwood Lumber Products (CorUd.) Oak J Plain-sawed, Red and White {Continued) Product Grades Squares Firsts & Seconds Sound No. 1, 2 Common Step Plank Firsts & Seconds Common Strips Clear Clear Sap No. 1, 2 Common Plank and Timbers Common Dimension No. 1, 2 Bridge Plank Common Timbers Sound, Square-edged Wagon Stock — Bolsters No. 1, 2 Sandboards No. 1, 2 Reaches. No. 1, 2 Poles No. 1, 2 Sawed Felloes No. 1, 2 Bending Oak Firsts & Seconds No. 1 Common Oaky Quarier'sawedy Red and White Lumber " Firsts & Seconds Selects No. 1, 2, 3 Common Strips Clear Clear Sap No. 1, 2 Common Hickory Lumber Firsts & Seconds No. 1, 2, 3 Common Wagon Stock — Axles No. 1, 2 Bolsters No. 1,2 Sandboards No. 1, 2 Reaches No. 1, 2 Eveners No. 1, 2 Poplar Lumber Panel Structural Timbers Sound, Square Edge THE GRADING OF LUMBER 169 Table 21. — Grades Adopted for Hardwood Lumber Products {CorUd.) Oak J Plain-^awedj Red or White (Continued) Product Grades Step Plank Firsts & Seconds (FAS) No. 1 Common Plank and Timbers — Construction Timbers and Plank Locomotive and Car Timbers Switch and Cross Ties Bridge and Crossing Plank Sheet Piling Cattle Guards Bumping Posts Wagon Stock — Bolsters • One Grade Sandboards One Grade Reaches One Grade Poles One Grade Sawed Felloes One Grade Bent Rims One Grade Wagon Spokes (White Oak) Second Growth, A. B. Dimension Material — Seat Stock One Grade Chair Frame Stock One Grade Table Tops One Grade Chair Backs One Grade Band-sawed Patterns One Grade Implement Stock — Plow Handle Strips One Grade Oaky Quarter-sawed J Red or White Lumber Firsts & Seconds (FAS) Selects No. 1, 2, 3, 4 Common Strips Clear Face No. 1, 2 Common Step Plank .Firsts & Seconds (FAS) No. 1, Common Hickory Lumber • Firsts & Seconds (FAS) No. 1, 2, 3, 4 Common Wagon Stock — Vehicle Wheel Stock A, B, C, D, E Axles No. 1 Bolsters One Grade 170 TIMBER Table 21. — Grades Adopted for Hardwood Lumber Products (Contd.) Hickory (Continued) Product Grades Wagon Stock {Cordinued) Sandboards One Grade Reaches One Grade Eveners One Grade Po'pLar Lumber Panel & Wide No. 1 Firsts & Seconds (FAS) Selects Saps Wide No. 2 No. 1, 2, 3, 4 Common Scoots Car Sign Boards One Grade Wagon Box Boards One Grade Shorts .No. 1, 2 Strips No. 1, Select No. 1, 2 Common Squares Firsts & Seconds (FAS) No. 1, Common Bevel and Drop Siding No. 1, Selects No. 1, 2 Common Dressed Dimension Strips No. 1 Selects No. 1, 2 Common Casing and Base Firsts & Seconds Saps and Selects No. 1 Common Flooring, Partition, and Ceiling No. 1, Selects No. 1, 2 Common Moldings No. 1, 2 Poplar, Quartered Lumber. Firsts & Seconds (FAS) No. 1, 2 Common Note. — Products and grades for oak, hickory, and poplar only are given in Table 21. Products and grades for other woods listed are similar. Comparison of the Rules. — The first rules for grading hard- woods adopted by the New York Lumber Association contained only a few grades applicable to all species and were compara- tively crude and unsatisfactory. The present rules of the Hardwood Manufacturers' Association contain about 300 grades, including rules for the inspection of all kinds of hardwood lumber and special forms, such as molding, partition, siding, flooring, etc. The rules now used by the National Hardwood THE GRADING OF LUMBER 171 Lumber Association containr about 400 grades, including all species and special forms. The comparative merit of the grading rules of the two as- sociations has been a mooted question for a number of years. Numerous attempts have been made to bring about an' agree- ment between the rival associations. Each association has tried to convince the other of the superiority of its rules and to per- suade the other to adopt them; and efforts have been made to bring about the adoption, on common, of a single set of rules. Every effort has failed, in spite of the fact that the members of both associations desire uniformity in grading hardwoods. The American Hardwood Manufacturers' Association, recently or- ganized to exploit hardwoods, is expected to be a strong factor in the movement to effect uniformity in rules. A comparison of the wording of the two rules seems to show that they are very similar. The chief difference is whether the grading is to be based upon the better side of the piece, the poorer side, or both sides. The National Hardwood Limiber Association rules formerly required inspection to be made on the poorer side of the piece; but now one regular and two special grades out of a total of seven are inspected on the face or best side. The Hardwood Manufacturers' Association requires both sides of the piece to be considered in determining the grade. The difference between inspection on the worse side and on both sides affects the whole of each rule so that the similarity of wording in other respects is misleading. It is obvious that inspection on the worse side is more satisfactory to the jobbers, and inspection on both sides to the manufacturers. Another difference is in the number of grades. The National rules include Firsts and Seconds, Selects, and Nos. 1, 2, and 3 Common, as well as special Nos. 1 and 2 Common Face; while the Manufacturers' rules provide for Firsts and Seconds and Nos. 1, 2, 3, and 4 Conmion, also Selects in oak and poplar. The following simimary of the rules of both associations is an attempt to pick out the fundamental requirements for the different grades, irrespective of species. It is, therefore, not to be considered as a grading rule for hardwoods, but is merely a brief, general summary of the principles involved, without regard to the innumerable details of exact inspection of specific kinds of woods. 172 TIMBER T OF THE Rules of the National Hardwood Lumber Association Note. — Inspection must be made upon the poorer side of the piece, except as otherwise specified. 1. Standard Lengths. Standard lecgths are from 4 to 16 feet inclusive in 1 foot multiples, but not over 15 per cent, of odd lengths are admitted. 2. Standard Thicknesses for Rough Lumber. yi in. ?8 in. IH'^ 2 in. H in. H in- IH in. 2J4 in. yi in. 1 in. l^i in. 3 in. The standard thicknesses of lumber surfaced on two sides are Ke in. less for pieces 1 in. and under, ^^2 in. less for pieces l>i in. and l}i in., and yi in. less for pieces 1 ^ in. and over. Surfaced lumber is measured on the basis of rough dimensions. 3Hin. 5 in. 4 in. 5Hin 4J^in. 6 in. 8. (a) Standard Grades. Firsts and Seconds Selects No. 1 Common {b) Special Grades. No. 1 Common Face No. 2 Common No. 3 Common No. 2 Common Face 4. Woods Included. Ash Cottonwood Pecan Basswood Cypress Poplar Beech Elm Red gum Birch Hackberr>' Sycamore Black gum Hickory Tupelo Buckeye Locust Walnut Butternut Magnolia Willow Cherry Maple Chestnut Oak 5. Description of Standard Grades. Grade Length Allowed Width Allowed Defects Allowed Firsts and Sec- 8 to 16 feet 6 in. and wider Ranging from no onds (Not : more defects in pieces than 20 re to 2 to 9 surface ft. be 1( ?ss than to 5 defects in 12 feet) pieces of 20 sur- face feet. THE GRADING OF LUMBER 173 Grade Selects No. 2 Common Length Allowed Width Allowed 6 to 16 feet 4 in. and wider (Not more than 30% to be less than 12 feet) No. 1 Common 4 to IG feet 3 in. and wider (Not more than ia% to be less than 8 feet) 4 to 16 feet 3 in. and wider (Not more than 10% under 6 feet) No. 3 Common 4 to 16 feet 3 in. and wider Defects Allowed Ranging from pieces 6 ft. and 7 ft. long, clear one face, to lar- ger pieces not less than Firsts and Seconds on best face and No. 1 Common on reverse. Must be clear in 4 ft. and 5 ft. lengths, and in 3 in. and 4 in. widths under 8 ft. long. Wider and longer pieces must work G6H% clear on from 2 to 4 cuttings. (No cutting less than 4 in. X2ft. or 3 in. X 3 ft.) Must work 50% clear face in from 3 to 5 cuttings accord- ing to width and size of piece. No cutting less than 3 in. X 2 ft. (In some woods cuttings required sound instead of clear.) Must work 25% sound cuttings. (No cutting less than IH in. wide nor less than 36 square inches.) 174 TIMBER Exceptions, — Firsts and Seconds for rock elm, hickory, and pecan are as follows: Grade Firsts and Sec- onds Length Allowed Width AUowed 8 to 16 feet 4 in. and wider (30% of 8 ft. t o 10 f t. lengths are allowed) Defects AUowed Ranging from clear pieces 4 in. wide to p'ec s with 4 defects in 18 surface feet. Firsts and Seconds for walnut and butternut are as follows: Firsts and Sec- 8 to 16 feet 6 in. and wider Ranging from 1 onds (Not more standard defect than 35% to and Ji in. sap be less than in pieces under 10 feet) 10 ft. long and under 8 in. wide to 3 defects and 3 in. of sap in pieces 10 ft. long and over by 12 in. wide and over. 6. Description of Special Grades. No. 1 Common Face grade is the same as Standard No. 1 Common, except that it is inspected from the better side. No. 2 Common Face grade is the same as Standard No. 2 Common except that it is inspected from the better side. Panel and Wide No. 1 (When combined must be at least 50% Panel) POPLAR, COTTONWOOD, AND GUM Grade Panel Width and Thickness 18 in. and over by % in. to 2 in. Lengths 8 to 16 feet Defects AUowed 50% of total quan- tity must be clear both sides; remainder may contain defects, provided 90% of the piece can be used for pan- els in cuttings 4 ft. long by the full width. THE GRADING OF LUMBER 175 Grade Width and Thickness Lengths Defects Allowed Wide No. 1 18 in. and over by 6 to 16 feet 6 ft. and 7 ft. J^ in. to 2 in. pieces must be clear; longer pieces must work 75% clear in 4 ft. and longer cuttings by full width of piece. 7. Standard Defects. Each of the following defines one standard defect: (1) One knot IJi in. in diameter. (2) Two knots not exceeding in extent of damage one IJi in. knot. (3) One split not diverging more than 1 inch to a foot, and not longer in inches than the surface measure of the piece in feet. (4) Worm, grub, knot, and rafting pin holes not exceeding in extent of damage one IJi in. knot. Summary op the Rules op the Hardwood Manufacturers' Association of the United States Note. — Both sides of the piec6 must be taken into consideration in making the grade. 1. Standard Lengths. Standard lengths are from 4 to 20 feet; 15 per cent, of odd lengths are admitted in any grade. 2. Standard Thicknesses for Rough Lumber. % in. 1 in. 2 in. 3 in. H in. IJi in. 2^ in. 3>i in. %m, IK in. 2Kin. 3H in. ?i in. li? in. 2?i in. 4 in. Ten per cent, of the shipment may be He in. scant. The standard thicknesses of lumber surfaced on two sides is %i in. less than the thickness of the rough lumber for pieces from >^ in. to to 1 in., %2 in. less for pieces % in., 1J4 in., and IK in., and K in. less for pieces 1^^ in. and over. Surfaced lumber is measured on the basis of rough dimensions. 3. Names of Standard Grades. Firsts and Seconds No. 3 Common No. 1 Common No. 4 Common No. 2 Common 178 TIMBER 7. Standard Defects. Each of the following is a standard defect: 1. One knot IK inches in diameter. 2. Two knots so located that the damage is not more than foi one standard knot. 3. Worm holes, grub holes, or rafting pin holes not exceeding in damage one standard knot. 4. Heart, shake, rot, dote, or any other defects not exceeding in damage one standard knot. 5. Bark or waney edge not more than 1 inch in average width and not extending more than one-third the length of the board. Must show on one side only. SOFTWOOD LUMBER GRADING General Character op the Rules for Softwoods The grading of softwood lumber is complicated by the large number of rules in use. Different kinds of wood, such as southern yellow pine, white pine, Douglas fir, etc., are graded under differ- ent rules. Some species are included under the rules of two different lumber associations. The grades adopted for the various kinds of softwood lumber by the principal lumber associations throughout the United States are shown in Table 22. Table 22. — Grades Adopted for Sopiwood Lxjmber Products by Principal Lumber Associations Southern Pine Association 1917 Rules for Yellow Pine (Longleaf, Loblolly, and Shortleaf Pine) Prodtict Grade Finishing A, B, C Panel Shop Flooring Flat Grain— A, B, C, D, No. 1, 2, 3 Common Edge Grain— A, B, C, D, No. 1 Common No. 1 Common Factory Ceiling A, B No. 1 & 2 Common Wagon Bottoms A&B Drop Siding A&B No. 1 & 2 Common Bevel Siding A&B No. 1 & 2 Common THE GRADING OF LUMBER 179 Table 22. — Grades Adopted for Softwood Lumber ^Produots by Principal Lumber Associations — (Continued) Product Grade Partition A&B No. 1 & 2 Common Molded Casing, Window, and Door Jambs . A, B & C Molding B & Better Common Boards, Shiplap, and Bam Siding. No. 1, 2, 3, 4 Common Grooved Koofmg No. 1 Common Fencin: •• No. 1, 2, 3, 4 Dimension and Heavy Joist No. 1, 2, 3 Common Lath No. 1 & 2 Timbers Select Structural Merchantable Square Edge & Sound No. 1 Common Georgia-Florida Sawmill Association 1916 Rules for Lumber and Planing-mill Products . (Same as Southern Pine Association Rules) IrUerstate Rules of 1905' and 1916* Yellow Pine Grcuie Product Flooring Boards Pianks Scantling Dimension Stepping Rough Edge or Flitch Prime Merchantable Standard North Carolina Pine Association 1917 Rules for Kiln-dried North Carolina Pine (Loblolly and Shortleaf Pine) Product Grade Rough and Dressed Lumber No. 1, 2, 3, Box, Culls Merchantable Red Heart Cull Red Heart No. 1 & 2 Shop No. 1 & 2 Baik Strips Box Bark Strips Flooring No. 1, 2, 3 & 4 Flat Grain No. 1 & 2 Rift ' Adopted by Georgia-Florida Sawmill Association, North Carolina Pine Association. * Adopted by Georgia-Florida Sawmill Association. 180 TIMBER Table 22. — Grades Adopted for Softwood Lumber Products by Principal Lumber Associations — (Continued) Product Grade CeiUng No. 1, 2, 3 & 4 Partition No. 1, 2, 3 & 4 Fencing No. 1, 2, 3 & 4 Base and Casing No. 1 & 2 German, Bevel and Drop Siding No. 1, 2, 3 <& 4 Rails No. 1 & 2 Molding No. 1 Factory Flooring and Roofers Same as Box Plank, Dimension and Timber One Grade Grades for air-dried are No. 1, 2, 3, Box, Culls, and Framing. Northern Pine Manufacturers' Association 1915 Rules for Northern White Pine, Spruce, and Tamarack Product Grade Thick Finishing 1st, 2d, 3d Clear A, B, C, D Select Inch Finishing Ist, 2d, 3d Clear . A, B, C, D Select D Stock & Box Siding A & Clear B, C, D & E Flooring A, B, C, D Flooring Farmer J Clear Flooring No. 1, 2, 3 Fencing (D & M) Shiplap, Grooved, Roofing, and D & M . . . No. 1, 2 <& 3 Factory Lumber No. 1, 2, 3 Shop Common Inch Shop Common Short Box Factory A Select & Better Factory B & C Select Thick Common Lumber Tank Stock Select Common No. 1, 2, 3, 4, 5 Common Common Boards and Strips No. 1 , 2, 3, 4, 5 Common Dimension No. 1, 2, 3 Lath No. 1 & 2 Fencing No. 1, 2, 3, 4 White Pine Association of the Tonawandas Rules for White Pine— Not Dat^d Product Grade Uppers Selects THE GRADING OF LUMBER 181 Table 22. — Grades Adopted for Softwood Lumber Products by Principal Lumber Associations — (Continued) Product Grade Fine Common No. 1, 2 & 3 Cuts No. 1 <& 2 Moldings Stained Saps Star Clear No. 1 Shelving & Dressing No. 2 Dressing No. 1 & 2 Shelving No. 1, 2 & 3 Bam No. 1 Box Bevel Siding Moldings Lattice Pickets Southern Cypress ManuJaxAurers' Association 1917 Rules for Cypress Product Grade Tank Stock One Grade Finishing A, B, C Factory Lumber Factory Selects Shop Boards Select Common Heart Select Common No. 1 & 2 Common Box, Peck Siding, Flooring, Ceiling A, B, C & D Shiplap, Casing, Base A, B, C & D Grooved Roofing, Partition A, B, C & D Switch Ties One Grade Cross Ties Standard No. 1 Peck Short Lumber B & Better Window and Door Frames, Jambs, Etc . . . B & Better Panel Stock B & Better Pickets No. 1 & 2 Battens and Squares One Grade Car Roofing and Siding C & Better Car Lining One Grade National Hardwood Lumber Assodaiion 1917 Rules for Cypress Product Grade Tank One Grade Finishing Firsts & Seconds Selects 182 TIMBER Table 22. — Grades Adopted for Softwood Lubcber Products by Principal Lumber Associations — {ContiniLed) Product Grade Factory Lumber No. 1 & 2 Shop Boards No. 1 & 2 Commons No. 1 & 2 Boxing Peck Finished Cypress A, B, C, & D Finish Panel B & Better Siding and Flooring A, B, C & D Ceiling and Partition A, B, C & D Car Roofing and Siding. C & Better Car Lining One Grade Battens and Squares One Gradfe Pickets and Lath No. 1 & 2 West Coast Lumbermen's Associaiion 1917 Rail Rules for Douglas Fir,* Sitka Spruce, Western Red Cedar, and Western Hemlock Product Grade Flooring No. 1, 2, 3, 4 Clear Edge No. 2 & Better, 3, 4 Clear Flat Grain Ceiling, Partition, Drop Siding, and Rustic. No. 2 Clear & Better No. 3 & No. 4 Clear Bungalow or Colonial Siding No. 2 Clear & Better Resawn Bevel Siding No. 2 Clear & Better No. 3 Clear Finish, Casing, and Base Selected Flat Grain No. 2 Clear & Better No. 3 Clear Boards and Shiplap Inch Select Common No. 1, 2, 3 Common Dimension, Plank, and Small Timbers Selected Common No. 1 & 2 Common Timbers Selected Common No. 1 & 2 Common Factory Lumber Factory Select & Better No. 1, 2 Shop Common Inch Shop Common Panel Lumber Stepping No. 2 Clear & Better No. 3 Clear Tank Stock One Grade. Windmill Stock Selected Common * Products and grades are given for Douglas fir only. Those for the other species listed differ. THE GRADING OF LUMBER 183 Table 22. — Grades Adopted for Softwood Lxtmber Products by Principal Lumber Associations — {Continued) Product Grade Silo Stock No. 2 Clear & Better Selected Common Well Tubing No. 3 Clear & Better Corn Cribbing No. 3 Clear & Better Selected Common Pickets One Grade Battens One Grade Mining Timber No. 1 Well Curbing Selected Common No. 1 Common Wagon Bottoms No. 2 Clear & Better Lath One Grade Turned Porch Columns No. 1 Ship Decking One Grade Turning Squares No. 2 Clear & Better Pipe Staves One Grade Pacific Lumber Inspection Bureau 1917 Domestic Rules for Douglas Fir,^ Western Hemlock, Sitka Spruce, Western Red Cedar, and Port Orford Cedar Product ' Grade Rough Clears No. 2 Clear & Better No. 3 Clear Finish, Casing & Base Selected Flat Grain No. 2 Clear & Better No. 3 Clear Boards and Shiplap Inch Selected Common No. 1, 2 & 3 Common Dimension, Plank, and Small Timbers Selected Common No. 1, 2, 3 Common Timbers Selected Common No. 1 & 2 Common Factory Lumber Factory Select & Better No. 1 & 2 Shop Common Inch Shop Common Panel Lumber Flooring No. 1, 2, 3, 4 Clear Edge Grain No. 2 Clear & Better, 3, 4 Clear Flat Grain Stepping No. 2 Clear & Better No. 3 Clear ^ Products and grades are given for Douglas fir only. Those for the other species listed differ. 184 TIMBER Table 22. — Grades Adopted for Softwood Lumber Products by Principal Lumber Associations — {Continued) ProdtLct Grade j^ O.J. J I No. 2 Clear & Better Ceiling and Partition [ J ' ' Bungalow or Colonial Siding No. 2 Clear & Better Resawn Tank Stock One Grade Cross Arm Stock One Grade Silo Stock No. 2 Clear & Better Selected Common Pipe Stave Stock One Grade Ship Plank One Grade Ship Decking One Grade Mining Timber One Grade Railroad Ties No. 1 & 2 Car Stakes One Grade Pickets No. 1 & 2 Lath One Grade Pacific Lumber Inspection Bureau 1917 Export Rules for Douglas Fir,* Western Hemlock, and Sitka Spruce Product Grade Rough Clears No. 2 Clear & Better Boards, Dimension, and Timbers Merchantable Common Flooring No. 1, 2, 3 Clear Edge Grain No. 2 Clear & Better & 3 Clear Flat Grain Ceiling and Rustic Siding No. 2 Clear & Better Stepping No. 2 Clear & Better Mining Timber One Grade Railroad Ties One Grade Ship Plank One Grade Deck Plank One Grade Pipe Stock One Grade Pickets One Grade • Staves No. 1 & 2 Lath One Grade 1 Products and grades are given for Douglas fir only. Those for the other species listed differ. . THE GRADING OF LUMBER 185 Table 22. — Grades Adopted for Softwood Lubcber Products bt Principal Lumber Associations — {Contintied) Western Pine Manufacturers* Associaiion 1917 Rules for Western White Pine/ Idaho White Pine,* Engeknann Spruce, White Fir, Western Red Cedar, Douglas Fir, and Larch Product Grade Finishing B Select & Better C & D Select Siding B & Better C, D&E Common Lumber No. 1, 2, 3, 4 & 5 Common Board and Strips Lath No. 1 Pine Lath No. 1 Mixed Lath No. 2 Lath Tank Stock One Grade Factory Lumber No. 1, 2 & 3 Shop Common Factory C Select & Better Inch Shop Common Short Box Dimension and Timbers No. 1 Cribbing One Grade Shiplap Drop Siding Beveled Siding Ceiling Grooved Roofing Flooring Calif omia White & Sugar Pine Manufacturers* Association 1916 Rules for Sugar Pine and California White Pine (Western Yellow Pine) Product Grade Finishing No. 1 & 2 Clear (or B Select & Better) C Select D Select Siding, Bevel B & Better C& D Flooring and Ceiling, Drop Siding B & Better C& D No. 1, 2 & 3 Fencing * Pinvs ponderosa, U. S. Forest Service name — Western Yellow Pine. * Pinus monticola, U. S. Forest Service name — Western White Pine. 186 TIMBER Table 22. — Grades Adopted for Softwood Lumber Products by Principal Lxtmber Associations — {Continued) Product Grade Factory Plank No. 3 Clear (or Factory C Select or No. 1 Cuts) No. 1, 2 & 3 Shop Inch No. 3 Clear Inch Shop Thick Common Select Common Boards and Fencing No. 1, 2, 3 & 4 Common Shiplap; Grooved Roofing, Drop Siding and D & M No. 1, 2 & 3 Common Lath No. 1 & 2 California Redwood Association 1917 Rules for Redwood Product Grade Uppers Clear Sap Clear Select Standard Sundry Commons Extra Merchantable Merchantable Construction Shop Common , Inch Shop Common Subflooring and Sheathing Stock Channel Rustic V Rustic Drop Siding Bevel Siding Battens Shiplap Pickets Northern Hemlock & Hardwood Manufacturers^ Association 1913 Rules for Hemlock Product Grade Boards and Strips Thick D & Better Inch Clear & Select Inch D Stock No. 1, 2, 3, 4 Common Piece Stuff or Dimension No. 1, 2, 3, 4 Dimension Lath No. 1 & 2 Flooring Ceiling Shiplap Drop Siding THE GRADING OF LUMBER 187 The various mills originally made their own rules to suit their special conditions. This might have been satisfactory where a mill supplied practically all the lumber used in its vicinity; but as soon as mills with different rules for the same timber began to sell in the same territory there was bound to be confusion and dissatisfaction. As means of transportation grew easier and cheaper and lumber was shipped greater distances from its source, organizations of manufacturers and dealers in different regions drew up rules to enable them to handle lumber in standard sizes and with less misunderstanding as to quality. By the use of such rules, manufacturers could tell more satisfactorily the quality of lumber wanted by dealers, and the dealers in turn could be surer that their orders would be correctly filled. These rules first classified the various kinds of lumber products, such as siding, boards, ceiling, flooring, finishing, dimension, etc., and then specified the size and number of defects, such as knots and checks, allowed in the various grades of each product. At first the rules were comparatively simple; but they have been expanded and new ones added to cover special products and the rules for each product further subdivided until pamphlets of 50 printed pages may be required to describe the different grades, sizes, and shapes of the various standard lumber products of one kind of wood. The most common defects specified in softwood grading rules are knots, stained sap, shake, wane, rot, pitch, splits, and season- ing checks. Inspection is usually specified on the better or dressed side. However, factory lumber used for the manufacture of doors, sash, etc., which must show on both sides, is graded from the poorer side. There is a tendency to avoid definite detailed specifications for the different grades, especially in certain of the white pine grading rules, in which only a general description of each grade and numerous examples of pieces that should be ad- mitted are given. In such cases, the grade of each piece may be left largely to the judgment of the inspector. Standard lengths and widths of softwoods differ somewhat under the various rules and also under different classes of material and grades in the same rules. In some sets of rules standard sizes are not listed completely. The various lumber products to which grades are given by the different lumber associations generally include finish, flooring, siding, ceiling, boards, timbers, fencing, etc. The methods used 188 TIMBER by various associations for describing the grades differ widely. In some rules the letters A, B, C, and D are used to designate grades of material for finish, ceiling, flooring, etc., and the num- bers 1, 2, 3, and 4, usually with the term ** common," are used for grades of common lumber, boards, dimension, etc. Other rules designate their highest grades of finish as 1, 2, and 3 Clear, either with or without lower grades of finish material designated A, B, C, and D. Description of Typical Rules for Softwoods Following is a description of the grading rules of a few of the most important species. SOUTHERN YELLOW PINE Southern yellow pirie includes longleaf, shortleaf, loblolly, and associated species of minor importance, such as slash and pond pine. The grading rules in common use are as follows: 1. Interstate Rules of 1905 and 1916, used principally in the southeastern United States and in Atlantic Coast markets. 2. Southern Pine Association Rules, used largely by Gulf State manufacturers for inland trade. 3. North Carolina Pine Association rules, used on the Atlantic Coast. 4. Gulf Coast Classification, used in export trade. Interstate Rules. — The Interstate rules of 1905 and 1916, which are used by the Georgia-Florida Sawmill Association for dimension and timbers, by the North Carolina Pine Association, and by lumber trade associations of the Atlantic Coast, are char- acterized principally by their simplicity. They are divided into three parts: General Rules, Classification, and Inspection. Seven classes of lumber are given: flooring, boards, plank, scant- ling, dimension, stepping, and rough edge or flitch; and the sizes are specified under each class. Under Inspection three grades are given: standard, merchantable, and prime. Prime is the highest grade. These grades are based on the number and position of defects and the amount of heart. The 1916 rules dif- fer from the 1905 rules in that they contain a density requirement. Southern Pine Association Rules. — The Southern Pine Asso- ciation rules for grades of yellow pine lumber are a revision of the THE GRADING OF LUMBER 189 old Yellow Pine Manufacturers' Association rules. Separate rules are issued for (1) lumber and dimension, (2) timbers, (3) car material, and (4) bridge and trestle timbers. 4 large number of different classes of products are given, such as finishing, floor- ing, ceiling, common boards, dimension, etc. The grades are defined under each of these classes. The letters A and B are used to designate the higher grades for finish and planing-mill products, and the Nos. 1, 2, and 3, with the term "common," are used for lower grades of planing-mill products, common boards, and dimension. Figure 103 shows boards of three grades. The requirements of each grade are not the same in the different classes of products; they vary with the sizes and requirements Tm. 108. — Boards of three (cradea — Southern Kne AsBOciation. of each class. In general, the material is graded from the face or better side. Grade A is practically free from defects on one side except in the greater widths. Grade B allows a few minor defects, such as splits, small knots, and pitch pockets. The Common grades allow larger defects and a greater number of them than A and B. No, 1 Common in general allows sound knots not over a certain diameter or smaller defects which do not impair its use; No. 2 Common allows knots not necessarily sound, not more than a certain specified diameter, and other defects if not too lat^e; No. 3 Common allows coarse knots, knot holes, and other defects, if they are not so injurious as to prevent the use of the lumber; No. 4 Common is "defective lumber." 190 TIMBER The Georgia-Florida Sawmill Association has reprinted the Southern Pine Association rules for lumber and planing-mill products in its rule book and now uses them for these items in place of the Interstate rules. The Southern Pine Association rules for timbers include the "density" rule prepared for structural material by the Forest Service. This rule requires a proportion of one-third summer- wood (the hard, dark colored parts of the annual ring) in the cross section and disregards botanical distinction. The grades given are No. 1 Common, Square Edge and Sound, Merchantable, and Select Structural Material, which is the highest grade. The first three of these grades may or may not include the density rule, the term "dense" being used to specify material conform- ing to the density rule and "sound" to include material without the density rule requirement. No. 1 Common Timbers are not required to conform to the General Timber Specifications, which exclude injurious shakes and unsound knots; but there are re- strictions on the amount of wane and size of knots for different sizes of material. Square Edge and Sound Timbers must be free from wane. Merchantable Timber must have approxi- mately two-thirds heart on the wide faces. The "Select Struc- tural" grade conforms to the Density Rule and also has restric- tions, recommended by the Forest Service, as to knots, shakes, checks, and cross grain. Wane is not permitted in this grade. There must be at least 85 per cent, heart measured around the girth anywhere in the length. North Carolina Pine Association Rules. — The grading rules for kiln-dried North Carolina pine adopted by the North Carolina Pine Association apply to lumber from 1 to 2 inches in thickness. The principal grades are Nos. 1, 2, 3, and 4 (or Box). No. 1 must be practically clear of defects up to 8 inches in width, ex- cept a limited amount of pitch streak; No. 2 grade allows a limited number of small sound knots and other small defects; No. 3 allows larger tight knots; and No. 4, or Box, contains large, reasonably sound knots and other smaller defects. There are also several minor grades which are largely cull and from which merchantable lumber can be cut with a specified maximum per cent, of waste. The grading rules for air-dried North Carolina pine are the same as for kiln dried except that 25 per cent, sap stain is allowed THE GRADING OF LUMBER 191 for No. 2, 50 per cent, for No. 3, 75 per cent, for No. 4, and 100 per cent, for Culls. The Shortleaf Pine Plank and Dimension Rules consist of a set of brief general rules defining a single grade for each of these classes of material. They are the ofiicial rules of the North Carolina Pine Association and a number of lumber trade associa- tions on the Atlantic Coast. GixM Coast Classification. — The Gulf Coast Classification of resawn lumber and sawn timber was first issued by the old Gulf Coast Lumber Exporters' Association and adopted in 1915 by the Southern Pine Association for export trade. Under " Resawn Lumber'' the diflFerent kinds of lumber are classified as flooring, boards and planks, deals, scantling, dimension, kiln-dried saps, and air-dried saps. Under each class the sizes are given and the grades, which are for the most part as follows: Special or Crown, Extra or French Prime, Prime, Standard or Genoa Prime, Mer- chantable, and Square Edge. The grades differ as to amount of heart and defects specified, and the same grade differs to a greater or less degree in its requirements in the different classes of ma- terial. Two other brief sets of rules are given, '* Usual South American or Standard River Plate" and "West Indian." Under "Sawn Timber" are brief rules adapted for use with this class of material. All these rules have high heart specifications in comparison to rules used in domestic trade. WHITE PINE— EASTERN OR NORTHERN Eastern or northern white pine {Pinus strohus) is sold under two sets of rules. The White Pine Bureau, St. Paul, Minnesota, composed of manufacturers of northern and western white pine, issued in 1917 a book^ containing the rules of the Northern Pine Manufacturers' Association and the White Pine Association of the Tonawandas, with several photographs of each grade and recommendations as to the use of each grade in house construction. Tonawanda Rules. — The Tonawanda rules were drawn up by the White Pine Association of the Tonawandas and are used in the Tonawanda wholesale district (Buffalo, Tonawanda, and North Tonawanda, N. Y.) and other eastern markets, principally on material brought by boat from the Georgian Bay District * This book contained also the rules of the Western Pine Manufacturers Association. 192 TIMBER and northern Minnesota. The rules contain grades as follows: Upper, Selects, Fine Common, Nos. 1, 2, and 3 Cuts, Nos. 1 and 2 Mouldings, Stained Saps, Star or Shaky Clear, No. 1 Shelving and Dressing, No. 2 Dressing, Nos. 1 and 2 Shelving, Nos. 1, 2, and 3 Barn, and No. 1 Box. The large number of grades allows considerable refinement in grading and provides grades especially suited for certain purposes. Common defects specified are knots, sap, sap stain, and shake. Particular uses for which each grade is suitable are given under each grade. Northern Pine Manufacturers' Association Rules. — ^The North- em Pine Manufacturers' Association rules are used, by manu- facturers throughout the Lake States. Under these rules several different classes of lumber are given, such as finishing, siding, flooring, fencing, conmion lumber, etc., and under each class several grades are given. In these rules, the better grades suit- able for finish are designated as 1, 2, 3 Clear and A, B, C Select, etc.; while the grades more suitable for other purposes are in- dicated as Nos. 1, 2, and 3 Common, etc. The grades 1, 2, and 3 Clear and A and B Select are f requentlj^ not sorted but simply sold together as B Select and Better. These rules differ consid- erably from the Tonawanda rules, so that a detailed comparison is difficult. Examples are given in the rules under each grade to illustrate different combinations of defects admissible. These rules apply also to Norway pine, spruce, and tamarack cut in the Lake States. DOUGLAS FIR Douglas fir is commonly graded under three sets of rules, one for rail shipments, one for domestic cargo shipments, and one for export. The rules are issued by the West Coast Lumbermen's Association and the Pacific Lumber Inspection Bureau.^ These are separate organizations which cooperate closely. The Pacific Lumber Inspection Bureau is in effect the inspection department of the West Coast Lumbermen's Association. West Coast Lumbermen's Association Rules ("Rail A"). — In the *'Rail A'' rules, there is a division into a large number of classes of lumber, such as flooring, ceiling, finish, common, dimension, timbers, etc., and a number of grades are given under each class. The principal grades are Nos. 1, 2, 3, and 4 Clear, 1 A small amount of Douglas fir is also graded by the rules of the Western Pine Manufacturers' Association (see Western Yellow Pine). THE GRADING OF LUMBER 193 Select Common, and Nos. 1, 2, and 3 Conmxon. The grade No. 1 Clear, however, is given only in vertical grain flooring and is practically free from all defects. No. 2 Clear admits a few small defects, which vary with the class of material. The "Clear" grades are finish material; while the "Common" grades are in- tended for other purposes, such as common boards and timbers. Defects allowable in "Common" grades are naturally more serious than those in the "Clear" grades. Grades of the same name under the different classes of material are somewhat similar as to defects allowed. There are often wide differences, however, both as to sizes and defects allowable due to a certain grade of lumber being adapted to particular use. Pacific Lumber Inspection Bureau Rules. — ^Two sets of rules. Export and Domestic, are issued for the use of cargo shippers. The two sets differ both as to classes of material and grades. There are a few grades, however, such as ship plank and flooring, which are practically the same in both sets of rules. Export Rules. — Several classes of lumber are given under the Export Rules, such afe clears, ship plank, deck plank, flooring, ceiling, siding, etc. Some of these classes have several grades and some but one. Boards are graded as No. 2 Clear and Better (Edge and Flat Grain), Merchantable, and Common. Flooring grades are Nos. 1, 2, and 3 Clear Edge Grain, No. 2 Clear and Better, Flat Grain and No. 3 Clear Flat Grain. Stave grades are Nos. 1 and 2. Other products are manufactured in one grade only. Domestic Rules. — In the domestic rules, a classification is made into rough clears, commons, factory lumber, flooring, ceiling, siding, etc., and under each class several grades are given, as Nos. 1, 2, 3, and 4 Clear, No. 2 Clear and Better, Nos. 3 and 4 Clear, Selected Common, and Nos. 1, 2, and 3 Common. These grades usually differ considerably under each of the different classes. No. 2 Clear and Better in general allows a small number of small tight knots and pitch pockets; No. 3 Clear allows a large number of larger knots and pitch pockets. In the "Common" grades larger knots, pitch pockets, colored sap, and other defects allowable in construction material are admitted. Specifications are given for a considerable number of products, such as tanks, cross-arms, silo and pipe stock, ship planks and decking, mining timber, and railroad ties. 194 TIMBER WESTERN WHITE PINE AND WESTERN YELLOW PINE Pinua numticola and Pinus ponderosa Western (Idaho) white pine and western yellow pine (called western white pine in the manufacturers' rules), larch, and Douglas fir cut in the Inland Empire (western Montana, Idaho, and eastern Washington and Oregon) are graded under the rules of the Western Pine Manufacturers' Association. They are nearly the same as the Northern Pine Manufacturers' Association rules for northern white pine; the higher grades of the Northern Pine Manufacturers' rules are omitted, however, and slight changes have been made in specifying defects, so as to adapt the rules to the western species. The grades designated as "Clear" and "A Select," in the Northern Pine rules, are omitted in these rules, so that "B Select and Better" is the highest grade of material. It admits small sound knots, slight stain, and slight traces of pitch or small season checks. Several examples are given in the rules under each grade for illustration. Western yellow pine throughout the southern Rockies, the middle Rockies, and the Black Hills is also graded under the rules of the Western Pine Manufacturers' Association. Western yellow pine cut in California and sold as California white pine is graded under the rules of the California White and Sugar Pine Association.^ SUGAR PINE Sugar pine in CaUfornia is graded under the rules of the Cali- fornia White and Sugar Pine Association. The rules are pat- terned after those of the Northern Pine Manufacturers' Asso- ciation. The highest grade, Nos. 1 and 2 Clear, is as nearly equivalent to the northern white pine B Select and Better as the timber characteristics of the two regions permit. No. 3 Clear is a cutting-up grade. Other grades are similar to the northern pine grades. California white pine (western yellow pine) is also graded under the California rules. Sugar pine and California white pine are separated in the Clear and Select grades but not in the Common grades which also include white and red fir. The common grades are used largely by California box manufacturers. * See Sugar Pine. THE GRADING OF LUMBER 195 HEMLOCK Western Hemlock, — In the Pacific Northwest western hemlock is graded under the "Rail A'' rules of the West Coast Lumber- men's Association and the Domestic and Export rules of the Pacific Lumber Inspection Bureau. In each rule the grades are practically the same as the Douglas fir grades; but hemlock products are Umited to flooring, ceiling, partition, siding, finish, boards, shiplap, and dimension. With the exception of timbers, western hemlock is made into the same forms of ordinary building lumber and planing-mill products as Douglas fir. In fact, in the grade of No. 3 Common for Douglas fir boards, dimen- sion, plank, and small timbers, part or all hemlock is allowed. Douglas fir mining timber may be 15 per cent, hemlock. In No. 3 Clear flat flooring and No. 2 Clear and Better ceiling, partition, and siding, 15 per cent, may be hemlock. In No. 4 Clear flooring and Nos. 3 and 4 Clear ceiling, partition, and siding, hemlock in any quantity is permitted. Eastern Hemlock. — In the Lakes States, eastern hemlock is graded under the Northern Hemlock and Hardwood Manufac- turers' Association rules and the Michigan Hardwood Manufac- turers' Association rules. Both sets of rules are modeled after the white pine rules used in the Lake States. The two rules differ somewhat but the common grades are similar. Finish has one or two grades. Boards and Strips are graded as Nos. 1, 2, 3, and 4 Common; and Piece Stuff or Dimension, as Nos. 1, 2, and 3. One rule has a No. 5 Board, the other a No. 4 Dimension. The other products made are flooring, ceiling, shiplap, and drop sid- ing, but no grades are listed. Hemlock in New England, New York, and Pennsylvania is graded largely by local rules, although Lake States grades are sometimes used in New York. In the local rules the grade "Merchantable" is frequently used and sometimes the grade "Mill Run Mill Culls Out." In West Virginia andNorthCaro- lina the Spruce Manufacturers' Association rules^ are followed to some extent. CYPRESS Grading rules for cypress are issued by the Southern Cypress Manufacturers' Association and the National Hardwood Lumber Association. ^ See Eastern Spruce. 196 TIMBER The present rules of the Southern Cypress Manufacturers' Association were designed especially for selling to retailers. The finish grades are A, B, and C, A having a perfect heart face. The grades for boards are Select Common, Heart Select Common, Nos. 1 and 2 Common, Box, and Peck. Flooring, siding, parti- tion, and ceiling grades are A, B, C, and D. One grade each is provided for tank stock, switch ties, cross ties, panel stock, shorts, battens, squares, car roofing, car siding, and car lining. The factory grades are Factory Selects and Shop. The National Hardwood Lumber Association rules for cypress are intended to serve both the retail and factory trade. The grades partake of the nature of both hardwood and softwood rules. The grades for rough lumber are Firsts and Seconds, Selects, Nos. 1 and 2 Shop, Nos. 1 and 2 Common, Nos. 1 and 2 Boxing, and Peck. Dressed finish is graded A, B, C, and D Finish. Siding, flooring, ceiling, and partition grades are A, B, C, and D. In addition there is one grade each for tank stock, car roofing, car siding, car Uning, battens, and turning squares. REDWOOD Redwood is graded by the rules of the California Redwood Association. The grades are divided into two classifications, Uppers and Sundry Common. Uppers are the finishing grades, and include Clear, Sap Clear, Select, and Standard. The Sundry Conunon grades are Extra Merchantable, Merchantable, Con- struction, Shop Common, Inch Shop Common, Subflooring, and Sheathing Stock. Merchantable is not a distinct grade. It is made up of 60 per cent. "Extra Merichantable" and the balance "Construction." The Shop Common grades are for factory use. These rules are used mostly for western trade, and a somewhat different set of rules is used for eastern trade. However, the eastern rules are not published by the Association but can be found only in price lists and are therefore difficult to refer to. The eastern grades are as follows: Product , Grade Finish Clear, A and B Ceiling Clear, A and B Drop siding Clear, A and B Rustic Clear, A and B THE ORADING OF LUMBER 197 Product Grade Porch flooring Clear, A and B Car siding Clear, A and B Car roofing Clear, A and B Siding (bevel, colonial, bungalow) Clear, A and B Clapboards Clear and Clear Sap Pattern stock Vertical Grain, Clear, and B Factory lumber Shop Squares Clear and A Tank stock Clear and Select Silo stock Clear and Select Pipe staves Clear and Select Boards and dimension Merchantable and Extra Merchant- able The Bigtree or Sequoia, of the same family as redwood, is sometimes cut for lumber, and this is often graded by the Red- wood rules. EASTERN SPRUCE Eastern spruce is graded in the Lake States under the rules of the Northern Pine Manufacturers' Association. In the New England States there is no published set of rules in use, but custom has brought about a general understanding of what is "Merchantable" and "Box." Sometimes spruce box lumber in New England is sold round edge mixed with round edge white pine. In the Adirondacks no published rules are available, but here again custom has made the following grades, which are currently quoted in New York City: No. 1 and Clear, No. 2, No. 3, Mill Run Mill Culls Out, and Mill Culls. In West Virginia and North Carolina the rules largely used are those of the Spruce Manufacturers' Association, which pro- vide for Firsts and Seconds (Clears), Selects, Dressing (Select Merchantable), Merchantable, Box, and Mill Culls. SITKA SPRUCE Sitka spruce is graded under the " Rail A" rules of the West Coast Lumber Manufacturers' Association and the Domestic and Export rules of the Pacific Liunber Inspection Bureau. The "Rail A" and Domestic rules have the following identical grades for spruce: B and Better finish. Factory Select and Better, Nos. 1 and 2 Shop Common, Inch Shop Common, and Nos. 198 TIMBER 1, 2, and 3 Box. As these grades indicate, Sitka spruce is used largely by door and box manufacturers. In addition, the " Rail A'' list provides for B and Better flooring, ceiling, partition, stepping, car siding and car roofing. A, B, and C bevel siding. Select and No. 1 Common, boards, dimension, planks, small timbers, and one grade each for squares, molding stock, panel stock, ladder stock, piano posts and sounding boards, and air- plane stock. The Export list provides No. 2 Clear and Better, No. 3 Clear and Better Shelving, Merchantable lumber and timber, and Merchantable Box. ENGELMAWN SPRUCE Engelmann spruce is graded under the rules of the Western Pine Manufacturers' Association. TAMARACK AND LARCH Throughout the Lake States tamarack is graded under the rules of the Northern Pine Manufacturers' Association. In the Inland Empire (Idaho, Montana, and eastern Wash- ington and Oregon) the rules of the Western Pine Manufacturers' Association are used for larch. SOUTHERN RED CEDAR (Juniperus virginiana) Red cedar lumber is usually sold log run, as there are no de- finite rules established. WESTERN RED CEDAR Western red cedar is graded under the rules of the West Coast Lumber Manufacturers' Association and the Pacific Lumber Inspection Bureau Domestic Rules. The rules covering western red cedar in these two sets of rules are nearly the same. The Bevel Siding grades are Clear A and B. Finish and boards are graded as No. 2 Clear and Better and Nos. 1 and 2 Common. One grade each is provided for bungalow or colonial siding, porch decking, flooring, porch columns, and newels. In the Inland Empire a few grades of the Western Pine Manufacturers' Asso- ciation are used to a very small extent. M> THE GRADING OF LUMBER 199 SOUTHERN WHITE CEDAR No standard rule is in general use for southern white cedar. Planking for boats is usually bought under the term ''Boat Boards." This is sound lumber in which knots are allowed, pro- vided they are tight. The Navy Department has prepared very satisfactory rules for southern white cedar boat boards. PORT ORFORD CEDAR The Domestic rules of the Pacific Lumber Inspection Bureau provide the following grades for Port Orford cedar: Nos. 1 and 2 Clear (B and Better), Selects, No. 3 Clear, Nos. 1 and 2 Shop, Common and No. 3 Boards, and Dimension. The products graded are boat boards, flooring, ceiling, siding, casing, base, partition, panel stock, shiplap, grooved roofing, and cribbing. The finishing and shop grades are similar to those for sugar pine, Caliifornia white pine, and Sitka spruce, with which Port Orford cedar competes. LODGEPOLE PINE In the Inland Empire the rules of the Western Pine Manu- facturers' Association are used for lodgepole pine. Very little of this species is graded, however, the great bulk of it being used for mine timbers and local consumption, for which there are no grading rules in general use. In the Rocky Mountain regions it is cut almost entirely by small mills, and no association rules are in general use for such material. WHITE FIR White fir, including several firs of minor importance, is sold in California under the common grades of the CaHfornia White and Sugar Pine Manufacturers' Association; in the Inland Em- pire it is sold under the common grades of the Western Pine Manufacturers' Association; and in Washington and Oregon it is admitted in the Douglas fir grade of No. 3 Common Boards. CHAPTER VIl LXTMBER PRODUCED AND USED IH THE UNITED STATES LUUBBR PRODUCED BY MILLS ■3 The annual lumber production of the United States is approxi- mately 40 billion feet. The cut reported for each of a number of years since 1899 and the number of active mills reporting are shown in Table 23. The total cut for the whole United States is given first, followed by the cut for each State, in the order of the quantity cut in 1915.^ The high point was reached in 1909. There has been little variation in the total cut in the last few years. Figure 104 gives the relative rank of the States leading in the production of lumber since 1850.* The rise and fall of the various States as lumber producers follows the shifting center of the lumber industry as forests are cut out and new areas are opened up. New York, Pennsylvania, Michi- gan, and Wisconsin all have held first place as lumber producers. Washington and Louisiana have ranked first and second respec- tively for the last ten years, ex- cept in 1914, when the order ■ See BuUelin No. 506, Department of Agriculture, "Production of Lumber, Lath, and Shingles in 1915," by J. C. Nellis. * Data are not available to make the diagram complete. 200 LUMBER PRODUCED IN THE UNITED STATES 201 was reversed. The large proportion of the total 1915 cut pro- duced in Washington and Louisiana is strikingly shown in Fig. 105, which gives graphically the 1915 cut by States. The quantity of each kind of lumber cut annually for a number of years since 1899 is given in Table 24. Yellow pine, which Billioiw of Board Feet 12 3 Wsihlngton Louiiiana Miiiiiiippi North Carolina- Arkantai Texas Oregon Alabama Virginia Wiiconiin CaliforDla ( Including Neyada) Florida Michigan Hlnaetota West VlrglDia- Halne Georgia Fenniylva&la — Soath Carolina. Tennettee Idaho Kentucky ITew Hampihirc. New York Ohio HiMOuri Indiana Montana Vermont Mattachaietts. Oklahoma Maryland Illinois Connecticut Arisona Colorado New Mexico New Jersey. Iowa Delaware Sooth Dakota I Wyoming Bhode Island. Utah "PiQ. 105. — Computed total lumber production in 1915, by States. includes the longleaf , shortleaf , and loblolly pines of the southern States, makes up about one-third of the annual lumber cut. Five species, yellow pine, Douglas fir, oak, white pine, and hemlock, have been the leaders in quantity production for the last twenty Table 23. — Total Number of AcrrvE Sawmills Reportino, "- '''l^r millB)'- ■•'Lsr mills) '"L-tSil" '37.011.aB9' a,05O,O00 2^300 ! 000 •'"'■" '"10 » s Mfttlb.m- > 37.345.023 jM/»e(fc m M/ttlb.m. '3S.158.41* i 1 27 United euitw .38,887,009 13 1 1 • 37,003,207 Bsii^'-;;:;;;:; 1 641 14C 71 i 547 hi SOS 1 163 1 i ■s 1 1 lOi 1 1U1 710 392 063 i 60S i i 517 i 71i 1 31 0£ f : 2i 1 01 80 575 290 |i S3 06 28 50 8S 1,048 58. m i 1 9( 7; 1 ^i( S6( 3S( 1 1 1 BOO i 5 1 000 a sj; 974 All other StM.« (') 786 LUMBER PRODUCED IN THE UNITED STATES 203 QoA(. nrv OF LcMBBR Repobted, BY Statbb, 1899-1915 laiO 131,034 Diilb|> I90B (46.S84 1908, (3I_.231 1B07 128,850 leoa 122,398 1904. 118,377 IS9i r31,8S3 mllV) >nill<)> mills] nUllB) Mfitlb.m. W /«((.. ™. M f^t b.m. Mf^lb.m. MMIb.m. M/eilb.m. M/Mth.m. MO.018.282 37,560.738 36,084.168 .im,*o2 : 3, ,; 2, .733 ,12a 20 73 1.. I,' 1,' M4 2. ,084 n 1;' ,,' I, :881 te 2!' 2, 3, ■IS I '■ ■; 1,' i.esi 2,094 3. 1457 rs 1.791 144 2, 1378 73 173 SOO n SflO IMl 1,13; HO 1, 1,2«I 1.734 1,62C 1,73! J72 2. „ 708 33 058 1.01f 47 1 968 es4 944 211 44' 6( 163 M 6S8 539 Oil W8 661 290 58( 37 77; 44^ 90 6« 760 SOI )7 W4 448 451 250 0B7 420 90i 99( 497 45( 774 50; 084 ss; 72; 754 432 )fl: m StM 790 W8 990 31S W 32i 645 284 351 D17 980 422 23 809 200 526 3W 331 26S 46' 34; 190 ao 15( 756 14( 015 49 737 3S 73 1S4 564 S34 786 2H 008 HE 108 489 168 71 Ml *S0 81 lot 093 7! 62 731 287. 72 56 060 B! 50 31 121 10 117 036 131 239 lie !12 s: S44 7) 880 542 )6 18 132 121 242 281 35; 46 41 184 892 44 487 3( 18 340 2! iS9 34 841 21 634 70 3t }3I 11 479 99< 83 25 88 l' DM ^; "1 ]; IS !? i '12 504 '15 946 ■ in 627 ■ 58S1 170 ••2; 24S I"24 ch, uid tbeM St*ta ai » iDoludn Aluka, Kan 9, Nebruka, Nevtulti, ai 204 TIMBER S 00 o o f-l CO So "Si® OtOOCOtPO t«oooc«o« cocoovHoo^Ob-or-i «peoc^le4 ioioeotocDiooc«eio.^oooa»tf»< ^ Oft £9 00 P rl CO CO CO W) *VQ >0 CO rl • 2(0 vM udco CO Kcoco<.-Nao ^»oa>* CO S^ CO ^s So*oo«oo ^oot>-r«oo ^ »-ip00!* :^? -^ •-i«c«c«ooco 04 94000 coo »OO»O»C0C«C0 »Hc»i'c^ioco»H coM«pr«'^r«iQ< NotoocoiocoeQu-^ coio»oo»o»owoor>^ o o> r^co CO CO o> CO ^FHjT^oo oo oj »h o ^ GO c« ^ to *H o M CO oe^ u) CO C4 OCO<-IU3 C*t*ui»OC*(X>*OC*Ci NC^r-ICO SCO 'I* sooco IS t« coco t« 0)t« t^^OMMOO OOOCO t^COO) •-i»ocor^^ ScoNooco^ oooiotoco •^ <1* N <1* CO "^ "^ cooJNcot*r^.i oocoQOiOor^) CO 00 o5 T(< ^ CO < t»oa)*o^^ •or>.oot*r^N*-"cO'i'>--< 00 CO 0» CO iOCO'1<*0»0»'lI"^"NCOe4 0>eO»ONO»00 05t>^0»CO r^'i-»0»-t( N00t(<( CO ^^ ^^ CD CO ^^ ^^ I0t0^i0<-Hp0000^^'-<«OAQCOOO*HO)C400 ooeoQ'iNOO q>coooJOO>ocqococ4N»-^^c 9>OOOCOtOC1'^>OC«f-<0»^0»COO)000»COO^ '«J<0»»-OC0C0NN CO»H CO »-•«-* C0»-iiO r^»Oi-< CO CON Clio CO goo «o f-t OCOO^CIO)COC0<-iCIOOCOOt»C«CO>OOO •-coor*r*co lO 0» O CO »0 1* lO 'l^ 'I* CO 'I* CO N CI CI "if-fCI 'I'COOO CO CO CI co>ooo" CI'*® IS l^eo ^ coco^^oooo O^^OOOCI r* CI 'I* »o CO r* C0^000i0i-t a)*0 ACOiOCO OOOOCIiOCl ci">OC0C0N»H CO CI 06 co^-co lO I I ^00 dcocir^^Q kOOtOCItOO Ot-^ojci^»ocq K»OQOodcood CO t* ^H CO 94 CO r* t-H CO f-H •^ ci » fh •• » * » ^»ocoeodf-H *-i »H o»r*OT»*'i^COOJOO '^^r »co»Hooq>co ■»00 CO »0 "I CO "I ^ SCO 00>OC1>OCOO '^IOCOCICItH r-ir^ OPtO CI cow CI CO 00 CI »o to r*cot>.eocO"^ '1J^t»CI^C0«^CI iiOO0»>OpO00c0'^^Ok0^CIC0C0k0>0 OOCliO > t* ^ 1-t CO p CO »o t* CO "1 00 oa CI 1-t eo ri d 04 »-tCi»o iCO»O»O«3T»*^C0C0CIC|f-Hi-4t-(.-it-(t-(i-4 ^•0004 , lOOOCIO o«-ipp»op ocor^ot-o r* 'i^ OJ t* CI 'i^ ^'I^CIClClr-l »H?H COOCO ^o« * » » cokor* CI04TJ* o ^ ■-« In O S V LUMBER PRODUCED IN THE UNITED STATES 205 years, and have furnished about three quarters of the total annual cut. Figure 106 shows the relative rank of the various species in the production of lumber for a number of years. The lumber production in 1915 by species is shown diagrammatically in Fig. 107.^ Table 25. — Reported Production of Lumber 1909, 1912, 1913, 1914, AND 1915 Computed Totals, by Classes op Mills Year Mills Quantity reported Class Number reporting Per cent. M ft. b. m. Per cent. Class 5: 10,000 M and over per year 1909 888 2.11 19,126,223 43.09 1912 926 3.19 21,259,274 54.29 1913 974 4.50 23,211,667 60.47 1914 867 3.15 20,934.446 56.06 » 1916 846 2.82 20,669,746 55.84 Class 4: 6,000 M to 9,999 M per year. . . 1909 783 1.86 5,291,606 11.92 1912 608 2.10 4,311,063 11.01 1913 740 3.41 4,303,122 11.21 1914 547 1.99 3,910,370 10.47 1 1916 453 1.51 3,224,448 8.71 Class 3: 1,000 M to 4,999 M per year. . . 1909 6,443 12.95 10,068,592 22.69 1912 3,747 12.92 7,009,608 17.90 1913 3,265 15.07 6,319,753 16.46 1914 3,291 11.97 6,078,730 16.28 1 1915 3,191 10.65 6,201,864 16.76 Class 2: 600 M to 999 M per year 1909 6,468 15.39 4,315,636 9.72 1912 4,420 15.24 2,951,068 7.54 1913 3,148 14.53 2,049.642 6.34 1914 4,261 15.49 2,780,184 7.44 » 1915 4,198 14.02 2,941,264 7.96 Class 1 : 50 M to 499 M per year 1909 28,459 67.69 5,582,738 12.68 1912 19,304 66.55 3,627,401 9.26 1913 13,541 62.49 2,502,825 6.52 1914 18,540 67.40 3,642,293 9.75 11915 21,263 70.99 3,974,334 10.74 All classes »1909 42,041 100.00 44,384,795 100.00 1912 29,005 100.00 39,158,414 100.00 1913 21,668 100.00 38,387,009 100.00 1914 27,506 100.00 37,346,023 100.00 1 1915 29,951 100.00 37,011,656 100.00 1 The data here shown for 1915 are the computed totals by classes of mills. ' The total for 1909 differs from that shown in other tables because 4,543 mills, cutting a total of 124,966,000 feet, or less than 50 M feet each, are omitted in this table. The proportion of the total cut produced by the different sized mills is given in Table 25 ^ It will be noted that the largest mills, i.e., those cutting 10 billion board feet and over per year, produced over half the cut in 1915, although they made up less than 3 per cent, of the total number of mills; while the mills cutting from 50,000 to 499,000 board feet per year, produced ^See Department of Agriculture, Bvlletin No. 508, "Production of Lumber, Lath, and Shingles in 1915," by J. C. Nellis, only about 10 per cent, of the cut and made up 70 per cent, of the total number of mills. The lumber-working plants, of all classes, consume annually some 2i}4 billion feet of wood. This is about 60 per cent, of the 2 annual lumber production. The ff I material is mostly lumber, but a 1 fis S includes comparatively small |£a ^s t^ ^jI g -< quantities of veneer, bolts, and 1-3 Isii-ss^u -?-"■'- a dimension stock. ga*5nel5aS«»oJwl3Ht5 '^ The average annual consurap- 1 1 I np^g- iii|,it.H 1 1 1 { * tion of wood by the wood-work- ,»«^.-.»,= ^ .^^ industries in the United States ° ia shown in Table 26.' The basic -I data were secured by a series of 3 State wood-using industry studies 1 conducted by the Forest Service 2 in cooperation with State organi- ,g zations. Although the State S studies were begun in 1909 and 'I were not completed until 1913, a g period of twelve months was made 'I the basis for the statistics for " each State, and the final figures ■S for the whole country presented "3 in Table 26 are a very good aver- g age of the demand of each industry e and of the demand for each kind ■3 of wood under normal conditions. § Lumber usually is remanufac- I. tured to a greater or less extent * before use, and in Table 26 the ri product of the sawmill is not eon- ^ sidered. However, planing mills operated in connection with saw- " mills manufacture lai^e quantities of Booring, ceiling, siding, finish, and other patterns which really are finished products, and such material accordingly is included. ' See Department of Agriculture, BuUetin No. 60S, " Lumber used in the manufacture of Woodea Products," by J. C. Nellia, LUMBER PRODUCED IN THE UNITED STATES 207 About 40 per cent, of the annual lumber cut is not worked by planing mills or factories into finished products. About one- fifth of this (in normal times) is exported, and the rest is used in Billions of Board Feet Tellow Pine DoQglat Fir Oak White Fine Hemlock Bprace Western Fine Cypress Maple Bed Gam Chestnat Yellow Foplar Sedwood Oedar Birch Larch Beech Batswood Elm Ash Cottonwood Tupelo White Fir Sagar Fine Hickory Balsam Fir Walnut Lodgepole Fine Sycamore All Other Kindt Fig. 107. — Computed total lumber production in 1915, by kinds of wood. general building and rough construction. Although all construc- tion lumber requires cutting to length to make it fit into place, this was not considered in the class of wood-working industries. 208 TIMBER Table 26. — Average Annual Consumption op Wood Industry Kind of wood Total Yellow pine White pine All industries , Planing-mill products, sash, doors, blinds, and general millwork Boxes and crates Car construction Furniture , Vehicles and vehicle parts Woodenware, novelties, and dairymen's, poulterers'} and apiaristers' supplies. . . Agricultural implements Chairs and chair stock Handles Musical instruments Tanks and silos Ship and boat building Fixtures Caskets and coffins Refrigerators and kitchen cabinets Matches and toothpicks Laundry appliances , Shade and map rollers Paving material and conduits Trunks and valises Machine construction Boot and shoe findings Picture frames and molding Shuttles, spools, and bobbins Tobacco boxes Sewing machines Pumps and wood pipe Pulleys and conveyors Professional and scientific instruments. . . . Toys Gates and fencing. .^ Sporting and athletic goods Patterns and flasks Bungs and faucets Plumbers' woodwork Electrical machinery and apparatus Mine equipment Brushes Dowels Elevators Saddles and harness Playground equipment Butchers' blocks and skewers Clocks Signs and supplies Printing material Weighing apparatus Whips, canes, and umbrella sticks Brooms and carpet sweepers Firearms Artificial limbs Tobacco pipes Airplanes Feet b. m. 24,676,656,564 13,428,862,066 4.550,016,430 1,262,090.371 944,677,807 739,144,483 405,286,436 321,239.336 289,790,660 280,234.571 260,196,026 225,619,686 199,598,228 187,132,848 153,394,657 137,616,266 85,442,111 79,502,040 79,291,575 76,067,000 74,667,997 69,459,430 66,240,200 65,477,783 65,148,190 64,127,476 59,946,527 55,826,938 35,862,900 35,070.928 28,926,552 27,450,540 25,191,907 24,299,403 21,112,342 20,313,450 18,188,910 16,987,697 12,878,986 11,980,500 10,018,680 9,218,000 9,064,812 8,197,050 7,894,249 6,888.366 5,324,794 5,021,550 4,946,880 2,277,334 2,093,901 687,080 489,515 74,300 Feet b. m. 8,610,685,624 6,447,780,805 1,044,993,123 678,114,162 18,926,400 31,205,478 18,566,406 98,463,396 20,000 67,000 2,107,994 41,291,700 66,698,652 11,612,366 11,970,650 7,872,931 1,397,000 1,150,000 65,092,000 15,277,990 22,461,088 ' '5,498,666 65,000 373,230 250,000 46,600 6,765,000 943,000 1,951,447 262,250 1,264,900 1,263,000 3,622,868 1,448,012 926,571 428,856 337,000 1,180,750 Feet b. m. 3,112,698,017 1,543,345,756 1,131,969,940 75,382,166 9,332,808 1,676,277 47,744,797 8,243,440 815,068 25,500 9,394,820 17,007,600 14,256,006 4,864,150 33.170.942 8,613,186 73,059,611 3,026,870 61,450,000 1,850,000 7,299,500 5,405,406 5,812,300 130,000 199,425 12,524,000 285,000 601,670 2,367,131 3,883,600 805,300 17,854,635 287,000 786,500 3,022,700 239.000 75,000 25.000 1,692,460 10,000 42,000 200,000 476,064 3,266,950 11,650 168,000 LUMBER PRODUCED IN THE UNITED STATES 209 BT THE Wood-working Industries op the U. S. Kind of wood — Continued DougUs fir Oak Maple Spruce Red gum Hemlock Feet b. m. 2,273.788.484 1,991.177,362 7,349,840 86,544.784 11,387,790 930,610 2,006,175 2,537,250 65,000 247.200 480,400 89,705,322 44,342.081 5.512.310 6.000 543.600 Feet b. m. 1,983,584,491 601,367,772 56,362.111 305,276,814 431,053,289 212,918,361 7,716,860 69.346,130 135.269,118 12.468.472 20,638,480 5,042,401 32,382.311 62,681.744 7,544,255 31,351,521 Feet b. m. 919,420,274 317.634,231 96,831,648 5,789,298 87,571,456 35,863,267 38,255,880 48,319.210 47,264.747 41.238.446 45.482,775 200,000 1,014,167 20,701,026 110,000 6,375,242 1,200,000 14,219,000 879,925 Feet b. m. 806.050,195 350.528.295 336,935,643 8,799,060 2,270,500 835,650 28,591,148 2,623.600 10.000 18.000 29.144,150 10,233,500 7,783,980 2,016,816 1,700.000 5,555,690 750,000 2,301,000 7,063,000 Feet b. tn. 797.343.658 121,366,583 402.121.640 1,035,640 102,237,867 26,650,314 8.358.290 11.976,000 8.790.280 6.654,300 9,243,825 1,085,000 164,000 6,491,170 7,010,520 13,483,400 Feet b. tn. 708,762,769 442,050.165 203,526,091 12,455,379 7,053,446 448,678 2,136,522 1,257,400 216.000 500,000 616,600 1,777,000 4,745,775 473,300 1,985.000 6,934,872 184,500 3.000,000 427,500 294.000 3,395,000 2,065,200 1.300,000 3,500,000 4,500 8,295,864 3.000 16.043.423 39.000 403,200 19,106,250 565,800 7,343,500 372,100 1,444,057 2,640,700 2.497.559 182,200 250.000 14,031,200 4,936,000 4,826,472 90.900 77.000 956,200 1,248,000 2,576.800 12,000 2,637,027 12,000 272.100 158,000 20.000 405.000 6,047.000 3.597,981 54,060,000 309,150 13,531,450 96.450 324,148 1,706,000 2,436,000 4,425.167 3,964,400 140,000 4,913.815 118,150 854.900 388.300 1.190,650 949.200 1,911.897 1,354.500 1,562,262 1,450,500 854.000 2,145.050 80.000 101.500 703,786 451,000 1,101.100 564.500 1,759,850 729,775 1,783,005 206,500 7,000,000 3,268,191 985,100 6,000 325,000 7,676.040 270,000 6,898,270 < 20,774,280 3,089.628 19,677.500 75.500 523,000 21.351,480 129,000 30,000 177,000 16.000 1,300 1,071,000 191,800 478,238 110,000 200,000 241.000 805.000 5,152,000 180,000 580.600 85.000 5i,090 150,000 1,000 325,000 416,000 202,500 250,100 284.800 15,000 138,000 1,980.700 257,600 2.328.750 415,200 73,000 1,003,800 130.500 1,078.500 30,000 1,750,000 37,000 200,000 15,000 1,000 100,000 36,000 10,000 1,060,000 102.900 1,820,000 5,000 20,000 110.000 345,000 - 147.100 ' 12,000 3,500 46,600 • ••■•••••••« 210 TIMBER Table 26. — Average Annual Consumption op Wood Industry Kind of wood Yellow poplar Cypress Western yellow pine Birch All industries. Planinff-mill products, sash, doors, blindis, and general millwork Boxes and crates Car construction Furniture Vehicles and vehicle parts Woodenware, novelties, and dairy- men's poulterers', and apiarists' supplies . . .^ Agricultural implements Chairs and chair stock Handles Musical instruments Tanks and silos Ship and boat building Fixtures Caskets and coffins Refrigerators and kitchen cabinets. Matches and toothpicks Laundry appliances Shade and map rollers Paving material and conduits. Trunks and valises Machine construction Boot and shoe findings Picture framed and molding. . Shuttles, spools, and bobbins. Tobacco boxes Sewing machines Pumps and wood pipe Pulleys and convenors , . . . Professional and scientific instruments Toys Gates and fencing Sporting and athletic goods. Patterns and flasks Bungs and faucets Plumbers' woodwork Electrical machinery and apparatus Mine equipment Brushes Dowels Elevators Saddles and harness Playground equipment Butchers' blocks and skewers. Clocks Signs and supplies Feet b. m. 680,936,848 236.047,697 165,416,737 32,439.064 63,374,680 48,666.960 7.278,889 12.412,300 1.140.000 211.900 40,371,926 240,000 448,077 14.674.881 9.640.860 5,986.729 600,000 1,026,200 326,000 2,988,600 2.208,677 190,000 2,168.814 701,000 7,368,919 8,039,244 1,974,000 400,000 1,001,400 882.000 6,000 970,200 344,330 8,010,000 819,000 561.700 86,600 282,265 334,600 22.200 85.000 Printing material Weighing apparatus Whips, canes, and umbrella sticks. Brooms and carpet sweepers , Firearms , Artificial limbs. Tobacco pipes. Airplanes 1,086.000 100,600 160.000 73,000 Feet b. m. 668.363,342 608,728,676 38,962,896 1,676,400 3,477,800 1,320,961 8,693,460 2,682,000 122,666 70,000 36,408,676 6,014,741 3,364,660 19,167,633 1,700,600 Feet b. m. 663,816.810 264.920,778 288,291,927 4,242,600 1,806,986 182,300 262,600 219,000 30,000 127,000 618,600 961,720 643,600 60.000 16.321.300 20,000 1,276,000 16,868,406 461,000 1,669,627 2.065.000 3.000 23.000 150.000 681,040 166,000 74,000 25,666 201,000 6,000 361,000 2,000 Feet b. m. 481,293,680 133,867,989 90,787,900 6,830,429 64,677,460 14,227,126 29,647,890 4,704,000 30,114,332 9,908,250 12,349,065 1,066,167 15,266,129 191.000 3,628.106 3,675.000 3.876.600 93,000 30,000 10,666 4,200 30,000 30,000 600 6,000 8,000 33,000 136,600 1,200 7,000 90,000 10,000 1.400 1.000.000 71,600 470.406 7.483,000 3,133,700 33,192,000 206,000 65,500 746,000 1,062,060 3,123.960 300,000 983,233 7,000 306,000 2,404,600 804,200 336,076 1,913,000 8.149,000 28.000 10,000 147,600 240.000 62.044 242.200 676.000 680.000 630,600 363,000 2.000 LUMBER PRODUCED IN THE UNITED STATES 211 BY THE Wood-working Industries of the U. S. — {Cordinued,) Kind of wood — Continued Hickory , Basswood Cottonwood Chestnut Ash Beech Feet b. m. 389,604,531 2,489,288 767,920 1,226,706 843,600 239,491,910 1,667,011 9,860,470 1,192,200 120,294,466 225 Feet b. m. 369,640,782 60,557,122 86,979,611 5,148,521 33,146,276 6,418,308 58,563,923 7,861,750 1,758,338 2.285,885 10,968,180 6,000 959,000 7,114,755 2,728,038 5,221,634 5,575,000 4,980,670 702,500 Feet 6. tn. 322,642,796 21,428,700 210,619,509 3,037,468 6,158,309 33,278,658 13,315,296 15,143,000 126,000 27,000 2,351,000 Feet b. m, 298,849,801 82.267.497 36.216.700 826.074 44,734,180 972,809 20,863,100 884,000 6.240,630 10,000 38.125,141 15,000 751,295 8,039,695 46,586,629 1,508,753 Feet b. m. 296,461,482 21,304,374 10.607,308 18.163,433 16,668,688 43,974,668 62,636.800 10,677,400 2,765,050 64,156,872 2,377,332 866.000 7,985.564 2,783.822 20,000 19.066.380 Feet b. m. 278,203,632 68,394,284 77,899,280 1,873,700 21,163,204 5,497,743 14,101,663 4,968,490 27,187,621 16,691,207 4,186,000 150,000 219,366 1,109,000 110,195 26,000 14,026 1,663,361 555,000 4,420,322 375,000 7.991.500 150,000 787,000 20,500 460,000 111.500 161,150 9 680.000 2,500 362.000 . 173,700 1,113,135 26,000 21,164,406 1,155,403 3,599,200 20,340,700 1,947,000 4,206,260 310,000 1,973,325 293,000 6,000 1,000 175,000 6,760 326,912 562,600 272,375 634,435 1,404,362 520,000 711,000 445.000 10,000 872.000 1,314,660 281.845 437,000 1,200,596 3,623,600 640,000 925,000 976,600 612,100 123,600 895,300 700 3,180,000 36,000 62,500 626,000 2,619,070 8,739,242 50,000 318,600 123,500 42,000 170 267,000 120,000 367,000 966,268 5,121,500 222,000 175,200 1,976,000 1,259.600 3,221,606 971,332 600 4,944,000 60,000 212,000 10.500 6,000 850.000 245,000 299,000 7.600 114,000 112.700 854,405 31,600 636,000 87,000 43,426 36,400 29,000 146,700 2,103.000 180,000 20,000 425.000 816,363 1.195.525 125,000 30,500 758,300 167,500 10,000 52,000 60.000 6,000 6,378,894 1.834.000 100 19,000 12,800 100,000 46,000 2.658.600 3.083.500 1,310.000 . 920.000 1,415,000 100,000 352,600 35,000 32,500 290,000 9,714 100,000 20,500 266,800 391,000 6,900 30,000 236,984 289.900 336.000 84,000 2.822.500 98.350 40,010 1,000 2,000 12,000 212 TIMBER Table 26. — Average Annual Consumption op Wood Industry Kind of wood Elm Tupelo Redwood Larch All -industries. Plamns-mill products, sash, doors, blinds, and general millwork Boxes and crates Car construction Furniture Vehicles and vehicle parts Woodenware, novelties, and dairy- men's, poulterers', and apiarists' supplies Agricultural implements Chairs and chair stock Handles Musical instruments Tanks and silos Ship and boat building Fixtures Caskets and coffins Refrigerators and kitchen cabinets. Matches and toothpicks Laundry appliances Shade and map rollers Paving material and conduits. Trunks and valises Machine construction Boot and shoe findings Picture frames and molding . . Shuttles, spools, and bobbins. Tobacco boxes Sewing machines Pumps and wood pipe Pulleys and conveyors Professional and scientific instruments Toys Feet b. m. 218,200.988 6,218,860 63,726,458 1,221,121 12,164,102 31,296,922 16.383,426 7,249,000 23,167,686 3,060,307 16,602,440 16,000 706,600 6,368,276 13,046,100 1,366,000 6,409,286 831,000 2,000 43,000 1,809,000 Gates and fencing Sporting and athletic goods. Patterns and flasks Bungs and faucets Plumbers' woodwork Electrical machinery and apparatus. Mine equipment Brushes Dowels Elevators Saddles and harness Playground equipment Butchers' blocks and skewers. Clocks Signs and supplies Printing material , Weighing apparatus , Whips, canes, and umbrella sticks. Brooms and carpet sweepers , Firearms , Artificial limbs. Tobacco pipes. Airplanes 20,000 200,000 200 2,042,066 166,000 3,226,760 40,000 66,000 463,000 8.800 187,000 176,000 68,600 276,000 334,000 200,000 84,200 Feet b. m. 127,968,309 17,003,448 74.982,910 114.168 2,629,000 1,067,600 5,366,900 1.140,000 191,000 460.000 20,000 138,490 248,000 600.000 39,600 3,842,000 1,006,000 1,060,000 27,600 240,000 260,000 10,376,217 2,200,000 629,500 639,000 12,000 5,000 20.000 500 3,589,760 1,000 15,000 20,000 1,000 322,816 10,000 Feet b. m. 122,326.779 92.759.619 2,439.600 120,000 355,250 259.000 3,208,150 200,600 286,200 8,124.938 837,600 1,074,710 1,782,000 161.000 13.000 2,000 58,500 47,632 1,033,200 2,000 Feet b. m. 114,029,275 88,484,081 7,470,300 1,537,669 154.000 36,000 147.460 20.000 416,700 100,000 9,745,000 328,626 2,000 56,000 4,475,000 61,000 16,000 9,117.600 512,000 31,220 133,000 48,000 700,000 LUMBER PRODUCED IN THE UNITED STATES 213 BY THE Wood-working Industries of the U. S. — (Continued.) Kind of wood — Continued Cedar Sugar pine Balsam fir Mahogany Spanish cedar Sycamore Feet h. m. 102,248,253 45.187,611 2,512,150 Feet b. m. 59.211,298 31,795,077 24,686,000 61,328 375,510 6,000 419,063 60,000 Feet b. m. 53,262.030 10.863.300 40,173,700 700.750 Feet b. m, 50,575,999 7,336,932 13,000 5,986,198 15,637,125 516,399 72,305 500 2,455,700 29,000 8,610.355 Feet b. m. 30,323.441 8.123 Feet b. m. 26.052,812 1.723.560 16.451.693 339,487 1.856.100 2.500 500 10.000 L.474.882 2.500 6.406,470 1,000 586,880 62,600 607,600 290,000 34,500 971,344 156,000 17,500 4,549.400 1,004,400 10,760 200,500 206,650 101,400 7.750 304,600 6,999.722 1.190.192 5,527,819 1,528,294 6,800 27.300 38,000 977,345 713,000 5,901,718 300 710,000 340,000 407,500 4,867.000 5,000 2,000 30,000 100,000 2,000 5,000 202,000 100,000 6,000 100 11.000 4.000 25,000 500 5.885 5,000 2.730 171.200 30.000 246.750 161.200 91.878 30.203.068 430.666 150.000 • 20.050,000 23.500 84.862 91,343 465,500 222,500 100,000 271,659 31.600 31.400 30,500 265.400 294.350 30.000 127,000 301,700 735.000 24,000 3.440 35,300 1,000 74,300 18,000 15.000 10,000 1,000 . 34,500 1 1,600,000 204.196 20.000 ( 1 48.500 4.000 16.000 1 1 1 2.000 i '""■ 30.600 270,000 • • • • 6,000 214 TIMBER Table 26. — Average Annual Consumption OP Wood Kind of wood Industry Black walnut Cherry White fir Willow All industries Feet b. m. 23,988.346 4,606.420 163,250 256.181 1,689,957 390,450 38,547 8,000 263,200 29,050 4,991.808 Feet b. m. 12,047,210 1,674,235 170,500 1,965,670 622,530 39,650 62,350 300 56,000 617,500 334.180 500 184.976 2,231,750 33,000 7,500 Feet b. TO. 11,338,580 8,162,250 3,142,080 Feet b. m. 10,664,770 Planine-mill products, sash, doors, blinojB, and general millwork Boxes and crates 266,000 10,004.600 Car construction Furniture 40.666' Vehicles and vehicle oarts 3,000 31,250 Woodenware, novelties, and dairy- men's, poulterers', and apiarists' supplies 128.000 Asricultural imnlements Chairs and chair stock • Handles 19.000 Musical instruments Tanks and silos Ship and boat buildine 3,750 660.635 474,000 1,000 Fixtures; 150.000 Caskets and coffins Ref rijrerators and kitchen cabinets . . . Matches and toothpicks Laundry appliances 20,000 2,000 2,000 2,000 Shade and map rollers Pavinff material and conduits Trunks and valises * Machine construction 10,817 60,600 25,000 10,000 5,000 Boot and shoe findings Picture frames and molding 125,004 Shuttles, spools, and bobbins Tobacco boxes Sewing machines 7,796,815 Pumps and wood DiDe Pulleys and conveyors . Professional and scientific instruments 71,200 732,750 2.000 Toys Gates and fencing Sporting and athletic goods 41,000 21,500 56,000 10,300 452,600 600 166,594 Patterns and flasks Bunes and faucets Plumbers' woodwork » . 92.400 27,800 Electrical machinery and apparatus. . Mine equipment Brushes 26.700 488.900* 10,000 Dowels Elevators Saddles and harness Plavfltround eauipment 15,000 Butchers' blocks and skewers Clocks 58,527 300,000 Signs and supplies Printing material 2,089.625 7,500 Weiehine apparatus Whips, canes, and umbrella sticks... . 20,000 600 1,700,135 Brooms and carpet sweepers Firearms Artificial limbs 10,000 56.170 Tobacco oipes Airolanes • LUMBER PRODUCED IN THE UNITED STATES 215 BT THE Wood- WORKING Industries op the U. S. — (Continued:) Kind of wood — Continued Dogwood Noble fir Magnolia Buckeye Persim- mon Cucumber Butternut • Feet h. m. 7,618»177 6,000 Feel b. m. 6,653,600 Feet b. m. 6,156,500 116,900 5,449,000 Feet b. m. 5,486,047 694.400 3,174,028 Feet b. m. 3,571,760 Feet b. TO. 2,660,700 1,416.800 624,000 Feet b. m. 2,310,793 231,700 6,653.500 678,000 1,300 477,100 9,500 415,000 63,419 83,700 36,000 16,000 3,800 660.000 1,100 693,500 11,500 34 159,000 1 10,000 1 20,546 .. 190,230 7,000 2,000 * ' " 6,666' 98,100 . 1 78,237 1 27,000 10,000 207,500 393,600 • 20,000 16,000 1 , 125,000 1 5,000 1 . 1 415,000 6,000 1 413,000 1 . . 214,000 20,000 7,060,425 1 2.909,760 75,000 1 1 1 10,000 10,000 31,200 1 30,000 10,000 6.000 " 206,000 1 3,000 42,710 1 ::::::::::: ::::;;...: j 14,600 ■ i ' ' ' * 147,288 1 9.000 2,000 1,000 ' 1.000 1 1 1 ***'** 67,000 ; 1 ■ ' ' ^ 75,000 1 1 1 1 1 1 1 1 ««•••■••••••• 1 i 1 ........ ..■■.■■. ..t. .......... .....■•■••■■•••••■•■••* ' 1 i 1 1 1 1 216 TIMBER Table 26. — Ayebaoe Annual Consumption of Wood Industry Kind of wood R«d alder All industries. I Lod^pole pine Red fir Circassian walnut Feel b. m. Feet b. m. Planing-mill products, sash, doors, blinds, and general millwork Boxes and crates Car construction Furniture Vehicles and vehicle parts Woodenware, novelties, and dairymen's, poulterers' J and apiarists' suppues Agricultural implements Chairs and chair stock Handles Musical instruments Tanks and silos Ship and boat building Fixtures Caskets and coffins Refrigerators and kitchen cabinets. Matches and toothpicks Laundry appliances Shade and map rollers Paving material and conduits. Trunu and valises Machine construction Boot and shoe findings. . . . . . Picture frames and molding. . Shuttles, spools, and bobbins. Tcbaeco boxes Sewing machines Pumps and wood pipe Pulleys and conveyors Professional and scientific instruments. Toys 2.248,700 1,979,500 436,000 792,500 20,000 625,000 361,700 969.500 1.000.000 1,000 8,000 1,000 5,500 Feet b. tn. 1,854,830 524.000 1,328.330 2,500 Feet b. m. 1,744,779 740,212 " ' 1,366* 452,040 16,820 14,857 8,366' 268,415 25.000 99.050 5»000 500 100 7,000 ' '256 Gates and fencing. .^ Sporting and athletic goods. Patterns and flasks Bungs and faucets Plumbers' woodwork Electrical machinery and apparatus. Mine equipment Brushes '. ^J\J^W"m™ •••«••••••••••••■■ ■ •■■••• • Elevators Saddles and harness Playground equipment Butcners' blocks and skewers. Clocks Signs and supplies 8 000 25,000 13,400 Printing material Weighing apparatus Whips, canes, and umbrella sticks. Brooms and carpet sweepers Firearms Artificial limbs. Tobacco pipes. Airplanes 20,500 47.035 LUMBER PRODUCED IN THE UNITED STATES 217 BY THE Wood- WORKING Industries of the U. S. — (Continued,) Kind of wood — Contintted Padouk Teak West Indian boxwood Alpine fir Locust Fee< 6. m. 1,386.530 333.792 ^eet b. m. 1,128.000 441,000 315,000 Feet b. m. 952,126 Feet b. m. 926,969 114.240 Feet b. m. 870,412 Feet b. tn. 780,000 270,000 500,000 Feet h. m. 639,228 220,000 723,063 31,000 1,690 230,100 70,000 100,000 150,000 593,663 2.000 1,000 110.350 1,000 • 2.100 10,000 60.500 3.000 1,500 37,566 70,328 4,000 . \ 8,375 10,631 785 764,309 1,125 1 215,028 85,000 6.000 1,000 1 1 ' 1 2,000 1 . . 1 961 2,500 1 . . . 103.440 , 1 72,300 37,236 1,000 653,848 , 1 \ 234,050 10,000 1,600 1,600 500 1 2.000 1 31,350 600 1 3.140 1 1 ' 46,000 ..........^. ........ 1 ' ' . 1 1 1 1 1 1 218 TIMBER Table. 26. — Average Annual Consumption op Wood Industry Kind of wood Horn- beam Ebony Oiage orange Rose- wood All industries. Planing-mill products, sash, doors, blinds, and general millwork Boxes and crates Car construction Furniture Vehicles and vehicle parts Woodenware, novelties, and dairymen's, poulterers', and apiarists' supplies Agricultural implements Chairs and chair stock Handles Musical instruments Feet h. m. 608.484 19,000 15,000 126,000 10,000 1,200 Tanks and silos Ship and boat building Fixtures Caskets and coffins Refrigerators and kitchen cabinets. Matches and toothpicks Laundry appliances Shade and map rollers Paving material and conduits. Trun& and valises 416,500 Machine construction Boot and shoe findings. . . . . . Picture frames and molding. . Shuttles, spools, and bobbins. "Tobacco boxes 100 Sewing machines Pumps and wood pipe Pulleys and conveyors Professional and scientific instruments. Toys Feet b. m. 528.812 50,600 5,450 1.045 4,664 60,373 1,800 1,330 500 Feet b. m. 520,076 30,000 1,000 439.026 50.000 50 Feet b. m. 471,734 6.100 37.000 15.280 1,100 3.613 15,456 40.645 1.600 52.925 1,000 2.420 "ioo' 219.353 Gates and fencing Sporting and athletic goods. Patterns and flasks Bungs and faucets Plumbers' woodwork 189,000 Electrical machinery and apparatus. Mine equipment Brushes Dowels Elevators 21,684 10.100 Saddles and harness Playground equipment Butchers' blocKs and skewers. Clocks Signs and supplies Printing material Weighing apparatus Whips, canes, and umbrella sticks. Brooms and carpet sweepers firearms 194,150 Artificial limbs. Tobacco pipes. Airplanes 9,800 24.400 10.642 1.000 2.260 12,656' 290 5,500 10.000 LUMBER PRODUCED IN THE UNITED STATES 219 BY THE Wood-working Industries of the U. S. — (Continued.) Kind of wood — Continued Prima vera Sassafras Eucalyp- tus Apple- wood Cocobola Yucca Holly Laurel Feet b. m. 380,568 121,973 Feet b. m. 360,268 336,000 Feet b. m. 338,800 4,200 Feet b. m. 320,935 Feet b. m. 279.400 Feet b. m. 172,300 60.000 3.500 Feet b. m. 86.680 500 Feet 6. m. 72,400 1.600 13.800 25.350 , 67.500 12,000 5,500 40,950 500 1,000 100 13,600 1,500 2,400 69,000 60,000 4,200 10,000 156,400 210,000 4,300 1.000 3.580 31,750 50 10.000 718 273,050 100 1,500 200 1 47.500 129.595 500 1 100 4,000 • 1 1 • 366* 1 . * 26,000 64,800 1 1 1 1,500 ■ ••••■ 2,000 21.000 ■ 1,000 ■ ■ ' 1 1 5,000 1 1 39,800 121,435 . 220 TIMBER Table 2C. — Average Annual Consumption of Wood by the Wood- working Industries of the U. S. — (Concluded.) Kind of wood Industry Satin- wood Koko Turkish box- wood Miscel- laneous foreign Miscel- laneous native All industries Feet b. m. 67,958 34,000 Feet b. m. 32,600 Feet b. m. 29.189 Feet b. m. 630,345 106.125 Feet b. m. 432.158 261,750 101,308 Planinff-mill products, sash, doors, blinds, and general millwork RrtXftfl And crates C!ar construction 288 22,070 32.000 46,000 46,580 330 Furniture 15 650 Vehicles and vehicle oarts 8,000 12 450 Woodenware. novelties, and dairy- men's, poulterers', and apiarists' suDolies - Aflrricultural imolenients 1 10,000 Chairs and chair stock 1 1 Handles 226 25 085 625 Musical instruments 5,100 Tanks and silos Shio and boat buildiniE .... ; ! 20,500 17,000 1,000 Fixtures 1,000 5,000 500 ::: • • • • • Caskets and coffins Refrigerators and kitchen cabinets. Matches and toothoicks . ■ • Laundry aoDliances Shade and mao rollers 100 1 • Pavinir material and conduits Trunks and valises Machine construction Boot and shoe findinss 1 Picture frames and moldins 1 2,250 40 36,600 Shuttles. sDools. and bobbins 1.575 Tobacco boxes 1 Sewinir machines . PumDS and wood oioe 1 • Pullevs and convevors Professional and scientific instru- ments Toys 1 Gfttes and fencinic Soortinir and athletic lEOods 1 1 • Patterns and flasks 1 1 Bunirs and faucets , Plumbers' woodwork 1 1 Electrical machinery and apparatus 1 i Mine eauioment Brushes 500 1,000 Dowels 1 Elevators 1 Saddles and harness Playflrround eauipment 1 Butchers' blocks and skewers ' Clocks 1 Siflcns and suoolies 1 Printing material 33 i 1 Weiehinff aoDaratus 1 Whins, canes, and umbrella sticks... 1 1 25,600 30 Brooms and carpet sweepers Firearms 1,731 Artificial limbs 30,000 322,280 Tobacco pipes ■ 22,000 Airplanes LUMBER PRODUCED IN THE UNITED STATES 221 All imported woods used by factories are included in Table 26. Wood used for lath, shingles, cooperage, veneer, pulp, dis- tillation, poles, and ties is not covered in Table 26. The scope of the statistics for the industries with titles that are not entirely descriptive is as follows: Planing-mill products cover standard patterns, such as flooring, ceiling, and siding, made in large quantities by planing mills in lumber-producing regions; while sash, doors, blinds, and mill work usually are made in mill work plants in the consuming regions. However, consider- able quantities of doors and door stock are made in the producing regions of the Pacific Coast States. Boxes and crates cover all kinds of packing boxes and crates made of lumber or veneer, also fruit and vegetable packages and baskets. Car construc- tion covers wooden construction in all types of railroad and elec- tric cars, as well as in locomotives and mine cars. Furniture includes household and office furniture, except chairs, kitchen furniture, and fixtures in business buildings. Vehicles take in horse vehicles, automobiles, bicycles; pushcarts, and wheelbar- rows. Woodenware and novelties embrace a thousand or more articles, such as kitchen utensils, wooden dishes, butter and cheese packages, measures, pails, wooden novelties of all kinds, ladders, and supplies for dairymen, poulterers, and apiarists. Fixtures are such as show cases, counters, bars, and lodge and church furnishings. Shade and map rollers include also curtain and rug poles and Venetian blinds. Machine construction means wooden construction in machinery of all kinds. Shoe lasts, pegs, and shanks are boot and shoe findings. Four-sevenths of the wood used for professional and scientific instruments went into pencils, the rest into artists', photographers^ and draftsmen's instruments, rules, and scientific apparatus. Billiard and pool tables, as well as gymnasium goods and all outdoor sporting goods, come under sporting and athletic goods. Mine equipment includes venti- lating apparatus, brattices, breaker equipment, slope rollers, and sprags. Dowels are small rods used in fastening together fur- niture, fixtures, and doors. Under playground equipment are included lawn swings and porch furniture. The kinds of wood are classified according to rather broad commercial practice. The classification is practically the same as that used in the lumber census bulletins; figures on the several 222 TIMBER species of each family or group are combined under the common name. Oak, maple, spruce, hemlock, birch, hickory, basswood, ash, elm, cedar, ^ willow, locust, and eucalyptus cover each its different species. Yellow pine includes the southern yellow pines, North Carolina pines, and minor eastern yellow pines. Western yellow pine is listed separately; trade names for it are western pine, western soft pine, and California white pine. White pine covers both northern and western (Idaho) white pine as well as Norway pine and jack pine. Cottonwood takes in the cottonwoods, aspen (or popple), and balm of Gilead. Tupelo includes cotton gum (called tupelo commercially), black gum, and water gum. Larch includes western larch and eastern tamarack. Mahogany covers all woods sold in this country as such. White fir includes the botanical white fir as well as grand and silver (amabilis) fir. The other minor firs, noble, red and alpine fir, usually sold as white fir, are listed separately. All other kinds of wood listed are single species, except that cypress, sycamore, cherry, dogwood, magnolia (cucumber, of the magnolia family, is shown separately), and buckeye are family names, but only one species of each is used commercially. Redwood sometimes includes lumber from the bigtree. The red-gum tree yields both commercial red and sap gum and both are covered in Table 26 by red gum. Figure 108 shows graphically the comparative amounts of wood used by the larger industries in each State. Amount of Wood Used Annually for all Purposes. — The average amount of wood used annually in the United States for the last few years for lumber and manufactured products has been about 52 billion board feet. This is made up of sawed lumber, ties, mine timbers, wood used for paper pulp, distillation, etc., but does not include fuel, fence posts, and rails. The total amount of wood used annually is estimated at about 100 billion board feet. Table 27 gives the quantities of wood used annually in the United States for various purposes. ^ Spanish cedar is listed separately. i LUMBER PRODUCED IN THE UNITED STATES 223 Table 27. — Amount of Wood Used Annually in the United States FOR Various Purposes^ Industry Quantity used annually Construction timber and lumber Planing-mill products, sash, doors, and general millwork . Boxes and crates Ties Mine timbers Pulp Car construction Shingles Furniture Vehicles Slack cooperage Distillation Lath Tight cooperage Veneers Wooden ware and novelties ' Agricultural implements Chairs Handles Musical instruments Tanks and silos Poles Ship and boat building Fixtures Caskets and coffins Refrigerators and kitchen cabinets Excelsior Miscellaneous secondary industries (39) and extract wood Total (lumber and manufactured products) Firewood Posts and rails Grand total * Based on 1912 lumber cut. Feet b. m. 14,484,568,000 13,428,862,000 4,547,973,000 4,501,767,000 2,422,375,000 2,154,025,000 1,262,090,000 1,203,769,000 944,678,000 739,124,000 655,603,000 610,680,000 543,833,000 478,438,000 444,886,000 405,286,000 321,239,000 289,791,000 280,235,000 260,195,000 225,618,000 204,000,000 199,598,000 187,133,000 153,395,000 137,616,000 100,247,000 1,195,110,000 52,382,134,000 42,968,000,000 6,000,000,000 101,350,134,000 INDEX Agencies that destroy wood, 65 Air dry condition, weight in, 12 wood, crushing strength for, 13 seasoning, 132 Alkahne soils, birds, and sap stain, 70 American Hardwood Manufacturers' Association, 171 American Society for Testing Mate- rials, 71, 72, 73 Amount of wood used annually in the United States, 223 Annual drain upon the forests, 9 growth of wood in the forests, 9 rings, 48 shrinkage as affected by direc- tion of, 128 Average annual consumption of wood, by species, in the United States, 208-220 Average annual consumption of wood by the wood working industries in the United States, 206 Average strength values for air sea- soned material compared to those for green material, 54 of green structural timbers, 44 Axe handle attacked by powder post borers, 68 Axles, maple and hickory, strength of, 115 B Beam at completion of test, failure in horizontal shear, 57 Bending, method of testing small beams in, 18 Bending strength, 123, 124 strength and dry weight, rela- tion between, 47 strength for western hemlock, 27 test, 16 Bending tests, effect of caseharden- .ing upon the moisture- strength curve, 31 Boards, badly warped, 132 Boiling process, effect of, 38, 39 Borers, fungi, and insects, 65 'Botanical and common names, 11 Boxes, nailed, wirebound, and dove- tailed, results of compres- sion tests, 99 packing, 97 wirebound, 106 Box-testing machine, revolving drum, 103 Box woods, classification of, 105 species for, 105, 106 Brashness, 132 Buggy shafts, oak and hickory, 112 summarv of tests on, 114 spokes, hickory, grades for, 108, 111 tests on, 111 method of testing, 108 spoke-test chart, 110 Buildings, deterioration in, 70 Casehardening, 129 Causes of decay, 63 Characteristics affecting decay in timber, 60 the strength of timber, 46 Character of lumbering industry, 9 Checking, 129 Checks and knots or knot holes, defects, 63 225 226 INDEX Classification of box woods^ 105 defects in structural timbers, 73 knots, according to form, 75 knots, according to quality, 74 species, 222 Cleavability test, method of making, 24 Collapse, 131, 133 Common and botanical names, 11 of species (table 3) facing page 10 Compression and drop tests of packing boxes, 97 parallel to grain, 19 relation between the crushing strength and moisture, 29 perpendicular to grain, 13, 20 Concrete as foundation material, 140 Conifers, common and botanical names of (table 3) facing page 10 Consumption of wood by species, 208-220 Cross arms, method of testing, 94 results of tests on, 96 test devised by the Forest Service, 93 Cross section of loblolly pine beams, 49 longleaf pine tree, 55 timber, 76 Crossties, poles and sawed timbers, 135 Crushing strength and moisture, 27 for air dry wood, 13 for green wood, 13 for western hemlock, 27 tests, results of, 27 Cubic foot weight, 11 Cultivator poles, Douglas fir and southern pine, 119 summary of tests on, 122 D Decay, causes of, 63 in timber, 65 characteristics affecting, 60 Deductions from tests, 42 of vehicle parts, 121 Defects, knots, checks, and shakes, 56 knots or knot holes and checks, 63 knots, stained sap, shake, wane, rot, pitch pockets, splits and seasoning checks, 162 Density, 46 or dry weight, 14 "Density rule," so called, 72 Deterioration in buildings, 70 Direction of grain, 50 Displacement of water, method of determining volume by, 25 Douglas fir and couthern pine culti- vator poles, 119 Drainage under lumber piles, 141 Drop tests and compression of packing boxes, 97 Dry kilns, preliminary treatments, 156 rot, 63 weight, moisture per cent, based on, 28, 29 Drying, kiln, 150 lumber, conditions suitable for, 157 theoretical conditions in kiln, 159 maximum rate of, 158 process of, 156 temperature of, 159 Durability and strength, 73 E Effect of absorption of water, 126 boiling process, 38, 39 casehardening upon the form of moisture, strength in bending tests, 31 moisture, 27 on strength, 52 preservative treatment, 36, 37 and conditioning treatments, 30 Effect of steaming process, 40 various treatments on small, clear sticks, 41 varying degrees of moisture, 28 INDEX 227 Elasticity, modulus of, 14 Elastic limit, fiber stress at, 13 Evaporation, rate of, 167 Failure due to spiral grain, 53 in horizontal shear beam at completion of test, 57 of nailed boxes, 100 Fiber saturation point and shrinkage, 126 stress at elastic limit, 13 Fir, Douglas, tests on, 31 Flat or horizontal piling of lumber, 138 "Forest growth" and "second growth," 121 Forest regions of the United States, 1,2 Forests, annual drain upon, 9 growth of wood in, 9 hardwood, 3 regional, 3 Foundation material, concrete as, 140 Fruiting body of wood-rotting fun- gus, 66 Fungi, insects, and borers, 65 Fungous growth, surface, 66 Fungus, spread of, by contact, 67 G Graded lumber, manufacture and distribution of, 164 Grades adopted for hardwood lum- ber products, 166 softwood lumber products, 178 Grades used for softwood lumber, 178 cypress, 181 Douglas fir, Sitka spruce, west- em red cedar, and western hemlock, 182, 183 Grades used for softwood lumber, Douglas fir, western hemlock, and Sitka spruce, 184 Engelmann spruce, white fir, western red cedar, Douglas fir, and larch, 185 hemlock, 186 kiln dried North Carolina pine, 179 lumber and planing mill prod- ucts, 179 northern white pine, spruce, and tamarack, 180 Port Orford cedar, 183 redwood, 186 sugar pine and California white pine, 185 western white pine, Idaho white pine, 185 whit« pine, 180 yellow pine, 178, 179 Grading of lumber by manufac- turers' associations, 162 structural timbers, 71 rules used for softwood lumber, 188-199 various, 77 Grain, compression parallel to, 19 perpendicular to, 13, 20 direction of, 50 spiral, 51 in Sitka spruce, 53 or diagonal, 52 Gravity, specific, 12 Green wood, crushing strength for, 13 structural timbers, average strength of, 44 Growth of wood, annual, in forests, 9 H Hardness, 14 method of making test for, 21 Hardwood associations, 165 Hardwood Manufacturers' As- sociation of the United States, 165, 168, 175 228 INDEX Hardwood associations, National Hardwood Lumber Association, 165, 166, 172 National Wholesale Lumber As- sociation, 165, 166 Hardwood lumber grading, 165 number of grades, 171 Hardwoods, common and botanical names (tables 3), facing page, 10 Heart wood and sap wood, 55 Hickory buggy spokes, grades for, 108, 111 toughness of, 123, 124 wagon axles after test, long- sleeved skein trussed, 117 thimble skein, 117 Honeycombed oak timbers, 131 Industries, miscellaneous, 208—220 using wood, 223 Insanitary method of handhng piling sticks, 144 mill yard, 143 Insects, fungi, and borers, 65 wood-boring grubs, powder post borers, white ants, 67 K Kiln, conditions in during a run, 158 Kiln dried lumber, 160 Kiln dry condition, weight in, 12 drying, 150 Kilns, types of, 151 compartment, 151, 154 spray, 153 progressive, 151, 152 blower, 152 Life of untreated wood species, 62 Loblolly-pine beams, cross section of, 49 Longleaf-pine, cross section of, 55 Lumber, dried, storage of, 160 grading, principles of, 162 rules for, 164 softwood, 178 kiln dried, 160 manufacture of in United States, 8 manufacturers' associations, principal, 163 piled lengthwise on wooden foundation, 139 piled sidewise on concrete and metal foundation, 139; so as to form "chimney," 147 piles, drainage under, 141 piling, dimension of stack (end- wise or sidewise piling), 146 (endwise piling), 145 foundations (endwise or side- wise piling), 145 roof protection (endwise or sidewise piling), 146 (sidewi&e piling), 145 spacing stacks (endwise or sidewise piling), 146 stickers (endwise or sidewise piling), 146 sun shields used to reduce checking, 147 treated ends (endwise or side- wise piling), 146 produced and used in the United States, 200 by mills, 200 production, computed total in • 1915, by kinds of wood, 207 States, 201 quantity of each kind reported, 1899-1915, 204 quantity reported and total number of active sawmills reporting by States, 1899- 1915, 202, 203 relative rank of States leading in production of since 1850, 200 INDEX 229 Lumber, relative rank of species leading in production since 1900, 206 reported production of 1909, 1912-1916 computed totals by classes of mills, 205 "round edge," 164 sawed, 138 used in the manufacture of wooden products, 206 yard of a sawmill in the Lake States, 149 Lumbering industry, character of, 9 M Manufacture and distribution of graded lumber, 164 of lumber in the United States, 8 Manufacturers' associations, grading of lumber by, 162 Maple and hickory wagon axles, 115 wagon axles after test, 116, 117 Marine borers, 69 Maximum load, work to, 14 rate of drying, 158 Mechanical properties of wood, 10, 15 Method of conducting drop test in boxes, 101 cutting and marking test mate- rial, 32 determining moisture content of wood, 24 specific gravity of wood, 25 volume by displacement of water, 25 making cleavabihty test, 24 making shearing test, 22 making test for hardness, 21 making test in tension at right angles to grain, 23 testing cross arms, 94 buggy spokes, 108 poles, 89 small beams in bending, 18 wagon axles, 113 wagon poles, 118 Methods of piling lumber for kiln drying, 155 test, 15 treatment, boiling process, 33 steaming process^ 33 Mills, lumber produced by, 200 Miscellaneous industries, 208-220 wood products, 221 Modulus of elasticity, 14 rupture, 13 Moisture and crushing strength, 27 condition of structural timbers, 61 content and cross section, rela- tion between, 127 composite curve of, 160 for several woods, 29 of wood, method of deter- mining, 24 effect of, 27 effect of various degrees of, 28 per cent, based on dry weight, 28, 29 Mushroom on a rotten log, 66 N Nailed, wirebound, and dovetailed boxes, 97 Names of species, common and botanical (table 3), facing page 10 Natural and . treated stringers, strength and stiffness of, 34 O Oak and hickory buggy shafts, 112 Oak, southern pine, and Douglas fir wagon poles, 118 Oak timbers, honeycombed, 131 Packing boxes, 97 Packing boxes, method of conduct- ing diagonal compression test, 98 230 INDEX PiUng lumber for kiln drying, methods of, lf»5 flat or horizontal, 138 rules for, 145 type of permanent foundation for, 141 Pith, position of, in cross section, 60 Pole drying lumber, 148 framework used to dry lumber, 149 Poles, results of tests on, 90 species tested for, 90 Powder post beetle, 68 Preservative treatment, effect of, 36,37 Products, miscellaneous wood, 221 Properties of various woods (table 3), facing page 10 Properties, mechanical, of wood, 10, 15 Q Quantity of each kind of lumber reported, 1899-1915, 204 Quantity of lumber reported and total number of active sawmills reporting by States, 1899-1915, 202, 203 R Rate of evaporation, 157 growth, 50 Redwood boards, bulge and collapse, 133 Regions, forest, 1, 2 Relation between amount of com- pression and crushing load, 30 bending strength and dry weight (fig. 23), facing page, 46 bending strength and dry weight, 47 crushing strength and moisture in compression parallel to grain, 29 moisture content and cross section, 127 Relations indicated by tests, 14 Resawed sections cut from case- hardened red-gum boards, 130 Resin in wood, 65 Results of crushing tests, 27 shearing tests, 58 tests on cross arms, species tested, 96 North American woods, 10 poles, 90 Revolving drum machine for testing boxes, 102 Right angles to grain, method of making test in tension at, 23 Rotting pine, 65 ''Round edge" lumber, 164 Rules, comparison of grading, 170 Rules for piling lumber, 145 Rupture, modulus of, 13 S Sapwood and heartwood, 55 Sawed lumber, 138 Sawed timbers, poles and crossties, 135 Sawmill products, grading of, 71 Seasoning chestnut poles, 137 Douglas fir timbers, 137 hardwood ties, 136 hemlock ties, 135 how wood may be injured in, 129 longleaf pine timbers, 138 methods, importance of proper, 125 northern white cedar poles; 137 northwestern ties, 134 objects of, 125 southern white cedar poles, 136 southwestern ties, 134 ties, 135 western red cedar poles, 136 wood, 125 "Second growth" and "forest growth," 121 Shakes, knots, and checks (defects), 56 INDEX 231 Shearing strength, 14 Shearing stresses, calculated, 59 test, method of making, 22 tests, result of, 58 Shipworms {mollusksy zylotryay and teredo) J 69 Shrinkage as affected by direction of annual rings, 128 and fiber saturation point, 126 per cent, of, 12 Softwood Associations, 178 California Redwood Association, 186 California White and Sugar Pine Manufacturers' As- sociation, 185 Georgia-Florida Sawmill Asso- ciation, 179 North Carolina Pine Associa- tion, 179 Northern Hemlock and Hard- wood Manufacturers' As- sociation, 186 Northern Pine Manufacturers' Association, 180 Pacific Lumber Inspection Bureau, 183, 184 Southern Cypress Manufactur- ers' Association, 181 Southern Pine Association, 72, 73, 178 West Coast Lumbermen's Asso- ciation, 182 Western Pine Manufacturers' Association, 185 White Pine Association of the Tonawandas, 180 Softwood lumber grading, 178 products and grade, 178-186 Softwoods, general character of rules for, 178 grading rules used for, 188 Cypress, 195 National Hardwood Associa- tion rules, 195 Southern Cypress Manufac- turers' Association rules, 195 Softwoods, Douglas fir, 192 Pacific Lumber Inspection Bureau rules, 193 West Coast Lumbermen's As- sociation rules (**Rail A") 192 Eastern spruce, 197 Northern, Pine Manufactur- ers' Association rules, 197 Spruce Manufacturers' As- sociation rules, 197* Engelmann Spruce, 198 Western Pine Manufacturers' Association rules, 198 Hemlock, western and eastern, 195 Michigan Hardwood Manu- facturers' Association rules, 195 Northern Hemlock and Hard- wood Manufacturers' As- sociation rules, 195 Pacific Lumber Inspection Bureau rules, 195 Spruce Manufacturers' As- sociation rules, 195 West Coast Lumbermen's As- sociation rules, 195 Lodgepole pine, 199 Western Pine Manufacturers' Association rules, 199 Port Orford cedar, 199 Pacific Lumber Inspection Bureau Domestic rules, 199 Redwood, 196 California Redwood Associa- tion rules, 196 Sitka spruce, 197 Pacific Lumber Inspection Bureau rules, 197 West Coast Lumber Manu- facturers' Association rules, 197 Southern red cedar (Junip- erus virginiana), 198 Southern white cedar, 199 Navy Department rules, 199 232 INDEX Softwoods, Southern yellow pine, 188 Gulf Coast Classification, 188, 191 Interstate rules, 188 North Carolina Pine Asso- ciation rules, 188, 190 Southern Pine Association rules, 188 Sugar pine, 194 California White and Sugar Pine Association rules, 194 Tamarack and larch, 198 Northern Pine Manufactur- ers' Association rules, 198 Western Pine Manufacturers* Association riiles, 198 Western red cedar, 198 Pacific Lumber Inspection Bureau Domestic rules, 198 West Coast Lumber Manu- facturers' Association rules, 198 Western Pine Manufacturers' Association rules, 198 Western white pine and western yellow pine, 194 Western Pine Manufacturers' Association rules, 194 White fir, 199 California White and Sugar Pine Association rules, 199 Western Pine Manufacturers' Association rules, 199 White pine, eastern or northern, 191 Northern Pine Manufactur- ers' Association rules, 192 Tonawanda rules, 191 Southern yellow pine, treated, tests on, 31 Specific gravity, 12 of wood, method of determin- ing, 25 Spiral grain, 51 failure due to, 53 in Sitka spruce, 53 Spiral grain or diagonal grain, 52 Springwood, 48 Spruce and pine killed by forest fires in the Rocky Mountains, 88 wood of, 51 Standing timber, 3 Steaming process, effect of, 40 Stiffness and strength of small pieces, 35 for western hemlock, 27 Storage of dried lumber, 160 Strength and durabiUty, 73 stiffness of natural and treated stringers, 34 bending, 123, 124 effect of moisture on, 52 of dry hickory, 123 maple and hickory axles, 115 small, clear pieces, 15 wood, 10 wooden products, 43 or mechanical properties of timber, 72 shearing, 14 Stress strain diagram for bending test, 16 Stringers, modulus of elasticity (stiffness), 36 rupture (bending strength), 36 small pieces cut from, 39 Structural material, vertical grained, 60 timbers, grading of, 71 moisture condition of, 61 strength of, 43 tests of, 70 working stresses permissible for, 87 Stum page, estimates, 5 Summary of grading rules, 172-178 of tests on buggy shafts, 114 cultivator poles, 122 wagon poles, 120 Summerwood, 14, 48, 72 Telephone poles, 88 Douglas fir {Psevdotsuga taxi- folia), 88 Engelmann spruce {Picea engel- manni), 88 INDEX 233 Telephone poles, Lodgepole pine {Pinus contorta), 88 Northern white cedar {Chamas- cyparis ihyoides)^ 88 Western hemlock (Tsuga hetero- phyUa), 88 Western red cedar (Thuja pli- cata)j 88 Temperature, humidity, and mois- ture in wood, 158 of drying, 159 Test, bending, 16 Test material, method of cutting and marking, 32 methods of, 15 Testing poles, method of, 89 Tests of structural timbers, 70 wirebound boxes, 107 on commercial material, 58 Douglas fir, 31 hickory buggy spokes. 111 nailed boxes, 104 structural timbers, telegraph poles, cross arms, packing boxes, and vehicle parts, 43 treated southern yellow pine. 31 relations indicated by, 14 Ties, seasoning, 135 Timber, characteristics affecting the strength of, 46 estimated stand in United States, 6 resources of the United States, 1 standing, estimates, 3 strength or mechanical proper- ties of, 72 supply of, 1 Toughness of hickory, 123, 124 Treatments, conditioning and pre- servative, jeffect of, 30 Various grading rules, 77 Chesapeake and Ohio Railway Company, 77 Chicago and Northwestern Rail- way Company, 80 Various grading rules, Chicago, Burlington and Quincy Railroad Company, 80 Chicago Great Western Rail- road Company, 78 Georgia-Florida Sawmill Asso- ciation, 82 Grand Trunk Railway System, 81 Illinois Central Railroad Com- pany, 81 Interstate rules of 1916, 85 National Board of Fire Under- writers, 82 Panama Canal, 82 Pennsylvania Railroad Com- pany, 80 West Coast Lumbermen's Asso- ciation, 84 Vehicle parts, deductions from tests of, 121 wooden, 107 Vertical grained structural material, 60 W Wagon axles, maple and hickory, 115 method of testing, 113 poles, Douglas fir, oak, and southern pine, 118 method of testing, 118 summary of tests on, 120 Warped boards, 131, 132 Water, effect of absorption of, 126 Weight in air dry condition, 12 kiln dry condition, 12 per cubic foot, 11 Western hemlock, bending strength, crushing strength, and stiff- ness for, 27 Wirebound boxes, 106 tests of, 107 Wood, agencies that destroy, 65 annual growth of in forests, 9 average annual consumption of, by wood working industries in United States^ 206 234 INDEX Wood, boring insects, white ants or termites, black ants, and carpenter bees, 68 Wood lice {cruataceanSy limnoriay cheluraj and 8phoBroma)j 69 Wood rotting, fungus fruiting body of, 66 Wood untreated, life of species, 62 Wooden products, lumber used in the manufacture of, 206 strength of, 43 vehicle parts, 107 Work to maximum load, 14 Working stresses ]>ermissible for structural timbers, 87 3 2044 102 887 247 This book should be returned to the Library on or before the last dieite stamped below. A fine of five cents a day is incurred by retaining it beyond the specified time. Please return promptly. DEC - ..JE AUG' 22150 MAR 19 1 951 C